The following lists some resources that might be useful for ID purposes.

Botany:

http://www.british-wild-flowers.co.uk/
http://www.ukwildflowers.com/index.htm
Mosses and Liverworts
R. Porley & N. Hodgetts, The New Naturalist Library.
ISBN 0-00-717400-4; pbk £25.00
The Wild Flowers of Britain and Ireland
The Complete Guide to the British and Irish Flora
Marjorie Blamey, Richard Fitter and Alastair Fitter
512 pages, 5000 col illus, 1600 maps.A & C Black
Softcover | 2003 | £16.99 | ISBN-10: 0713659440
Fully illustrated and mapped guide to the British and Irish flora. Unlike its predecessors, it is however restricted to Britain and Ireland.
Orchids of Britain and Ireland - A Field and Site Guide
Anne Harrap and Simon Harrap
352 pages, 250 col photos, maps. Christopher Helm
Softcover | 2005 | £29.99 ISBN-10: 071366956X
Well illustrated orchid guide, covering the identification, biology and conservation of every species of British and Irish orchid
Field Flora of the British Isles
Clive Stace
736 pages, 16 b/w illus, 12 figs. Cambridge University Press
Softcover | 1999 | £22.99 |ISBN-10: 0521653150
The first modern portable guide for those wishing to identify plants growing in the wild in the British Isles. Based on the author's now standard work, New Flora of the British Isles (2nd edition, 1997), this abridged version offers the same complete coverage and user-friendly features in a compact format
The Wild Flower Key
How to identify wild flowers, trees and shrubs in Britain and Ireland
Francis Rose and Clare O'Reilly
480 pages, col plates, line illus. Frederick Warne Books
Softcover | Edition 2 | 2006 | £19.99 ISBN-10: 0723251754
Revised and expanded edition of this essential guide with full keys to more than 1600 wild plants found in Britain and Ireland.
British Mosses and Liverworts
EV Watson
519 pages, 242 line illus, 17 b/w photos. Cambridge University Press
Softcover | Edition 3 | 1981 | £43.00 | ISBN-10: 0521285364
An introductory book giving full descriptions and ecological details of over 200 of the commoner species, illustrating each to show its diagnostic microscopic and macroscopic features
Colour Identification Guide to the Grasses, Sedges, Rushes and Ferns of the British Isles and North-Western Europe
Francis Rose, Illustrated by Claire Dalby, Lura Mason and R B Davis 204 pages, col and b/w illus. Viking Books
Hardcover | 1989 | £50.00 | ISBN-10: 0670806889
This comprehensive work provides amateurs and professionals alike with a definitive account of all the native and naturalized species of grasses, sedges, rushes and ferns
Lichens: An Illustrated Guide to the British and Irish Species
Frank S Dobson
480 pages, col photos, illus, distrib maps. Richmond Publishing
Hardcover | Edition 5 | 2005 | £45.00 | ISBN-10: 0855460954
Softcover | Edition 5 | 2005 | £35.00 | ISBN-10: 0855460962
Standard British work on lichens covering 450 of the most common species and a selection of the rarer ones.
Pocket Guide to Mushrooms and Toadstools of Britain and North-West Europe (new edition)
Marcel Bon
368 pages, 1200 colour illustrations. Christopher Helm
Softcover | Edition 2 , due 2007 | £14.99 | ISBN-13: 9780713674583
Dr Roy Watling, past President, British Mycological Society says “Superbly illustrated, highly informative, the best kind of field guide. Mr Bon has given us an excellent and beautiful book.'.“ The guide to over 1500 reasonably-sized species with gills or tubes covers all those that are likely to be seen in Britain, Ireland or in Europe north of the Alps and Mediterranean zone. It is fully keyed, and illustrated throughout with scrupulously accurate colour paintings and spore drawings
Collins Tree Guide
Owen Johnson and David More
464 pages, 216 col plates. Harper Collins
Hardcover | 2004 | £25.00 | ISBN-10: 0007139543
Softcover | 2006 | £16.99 | ISBN-10: 0007207719
Published in the same format as Collins Bird Guide, the Collins Tree Guide is a fully-illustrated guide to the trees of Britain and non-Mediterranean Europe.

Marine Life

Photographic Guide to Sea and Shore Life of Britain and North-West Europe
Ray Gibson, Ben Hextall and Alex Rogers
Series: OXFORD PHOTOGRAPHIC GUIDES
436 pages, 486 col photos, 903 line illus, maps. Oxford University Press
Softcover | 2001 | £16.99 ISBN-10: 0198507097
Guide to the animals and plants of the sea-shore in North-West Europe. Each species is illustrated with a photograph, and in most cases is accompanied by a line illustration that emphasises the critical features for identification and a map.
Marine Fish and Invertebrates of Northern Europe
Frank Emil Moen and Erling Svensen
608 pages, 1000 col photos. AquaPress
Hardcover | 2004 | £36.95 ISBN-10: 0954406028
The main section of this book presents the animal species in a natural systematic order. Colour photographs taken in their natural environment.
Keys to the Freshwater Fish of Britain and Ireland: with notes on their distribution and ecology (2004).
Peter S. Maitland - Freshwater Biological Association
248 pp. ISBN 0-900386-71-1. pbk 22

Zoology

Collins Field Guide to the Mammals of Britain and Europe
David MacDonald
384 pages, 64 colour plates [by Priscilla Barrett], col line illus, maps. Harper Collins
Hardcover | 2005 | £25.00 | ISBN-10: 0002197790
Re-release of David MacDonald's field guide to over 230 species of mammal found in Europe and the surrounding seas.
Which Bat Is It?
A Guide to Bat Identification in Great Britain and Ireland
RE Stebbings
48 pages, b/w illus.Mammal Society
Softcover | £3.50 ISBN-13: 9780906282199
Excellent little guide to bats, giving identification key, advice on how to study bats and an important section on legislation
A Guide to British Bats
Kate Jones and Allyson Walsh
Series:  FIELD STUDIES COUNCIL OCCASIONAL PUBLICATION 65
8 pages, col photos, b/w illus, tabs.Field Studies Council
Unbound | 2001 | £2.50 ISBN-10: 1851538755
Britain is home to 16 species from 2 families (Rhinolophidae and Vespertilionidae). This fold-out guide includes all 16 species of bats that live and breed in Britain
Collins Bird Guide
Lars Svensson, Killian Mullarney, Dan Zetterstrom and Peter J Grant
392 pages, 3500 col illus, 700 maps. Harper Collins
Hardcover | 1999 | £24.99 | ISBN-10: 0002197286
Softcover | 2001 | £16.99 | ISBN-10: 0007113323
Covering Britain and Europe, the book provides all the information needed to identify any species at any time of year, with detailed text on size, habitat, range, identification and voice
Collins Field Guide to the Reptiles and Amphibians of Britain and Europe
Nick Arnold
288 pages, 49 col plates, b/w illus, maps. Harper Collins
Hardcover | Edition 2 | 2002 | £25.00 | ISBN-10: 0002199645
Describes and illustrates all the British and European species of Salamander, frogs and tree frogs, toads, tortoises, turtles, and terrapins, geckoes, agamas, lizards, and chameleons, slow worms, skinks, amphisbaenians and the 25 species of snake.
Key to the Freshwater Fish of Britain and Ireland, With Notes on their Distribution and Ecology
Peter S Maitland
Series:  FRESHWATER BIOLOGICAL ASSOCIATION SCIENTIFIC PUBLICATIONS 62
248 pages, 48 col plates, b/w illus, maps. Freshwater Biological Association
Softcover | 2004 | £23.50 | ISBN-10: 0900386711
Based on Peter Maitland's earlier Key to British Freshwater Fishes, published by the FBA in 1972, this new edition has been extensively enlarged and updated. Fifty-seven species are recognised in a checklist for Britain and Ireland, including several new species such as Black Bullhead, False Harlequin and Sunbleak, which have recently become established in Britain.

Invertebrate

Pocket Guide to the Insects of Britain and Western Europe
Michael Chinery
320 pages, 2000 col illus. A & C Black
Softcover in preparation - due 2007 | £14.99 | ISBN-13: 9780713672398
The text summarises key identification points, and introductory sections for each group covered give useful guidelines on the characteristics of the orders, families and genera covered
Collins Complete British Insects
Michael Chinery
384 pages, photos.Harper Collins
Softcover | 2005 | £16.99 | ISBN-10: 0007179669
A photographic field guide to all the common and some unusual species of insects across Britain that the keen amateur naturalist is likely to spot. Approximately 1,500 species are illustrated with clear photographs chosen for their help in identification. It provides details of distribution for each insect, and whether it is common or rare, and includes photographs of larvae. Insect groups dealt with include butterflies and moths, mayflies, dragonflies, damselflies, grasshoppers, crickets, earwigs, lacewings, bugs, bees, wasps, ants and beetles, all with keys to ensure accurate identification.
Pocket Guide to Butterflies of Great Britain and Ireland
Richard Lewington
144 pages, 450 illus. British Wildlife Publishing
Softcover | 2003 | £9.95 | ISBN-10: 0953139913
Identifies all the resident and migrant species of butterfly that have occurred in Great Britain and Ireland
Collins Field Guide to the Butterflies of Britain and Europe
Tom Tolman and Richard Lewington
320 pages, col Illus, dist maps. Harper Collins
Hardcover | Edition 2 | 2004 | £25.00 | ISBN-10: 0007189915
Covering the whole of Europe and North Africa. In all 440 species are covered, with each species fully illustrated with paintings of the male, female and all major forms, varieties and sub-species. Distribution maps accompany every widespread species with maps
Butterfly photos from http://www.butterfly-conservation.org/
Field Guide to the Moths of Great Britain and Ireland
Paul Waring and Martin Townsend with illustrations by Richard Lewington.
432 pages, col photos, 1800 col illus.British Wildlife Publishing
Hardcover | 2003 | £45.00 | ISBN-10: 095313993X
Softcover | 2003 | £29.95 | ISBN-10: 0953139921
First field guide to illustrate and describe all the British and Irish macro-moths showing the species in their natural resting posture.
Colour Identification Guide to Moths of the British Isles (Macrolepidoptera)
Bernard Skinner
276 pages, 43 col plates, illus. Viking Books
Hardcover | Edition 3 | 1998 | £50.00 || ISBN-10: 0670879789
Covers over 800 species and enables the entomologist to identify all the larger moths
Moth photos http://ukmoths.org.uk/
The Colour Identification Guide to the Caterpillars of the British Isles (Macrolepidoptera)
Jim Porter
275 pages, 49 pp col photographs. Viking Books
Hardcover | 1997 | £50.00 | ISBN-10: 0670875090
A comprehensive, illustrated guide to the caterpillars of British butterflies and macro-moths has been produced to complement Bernard Skinner's Colour Identification Guide to the Moths of the British Isles. This book illustrates over 850 different species, all photographed in natural situations upon the relevant foodplants
Identify caterpillars at http://www.whatsthiscaterpillar.co.uk/
British and Irish Pug Moths: A Guide to their Identification and Biology
AM Riley and G Prior
264 pages, 12 col plates, 300 figs, 49 maps. Harley Books
Hardcover | 2003 | £29.50 | ISBN-10: 0946589518
Descriptions of the biology and characters of all stages of the 52 species from Britain and Ireland, with maps showing the known distribution of each species on a vice-county basis.
British Pyralid Moths
A Guide to their Identification
B Goater
176 pages, 9 col plates.Harley Books
Hardcover | 1986 | £22.50 | ISBN-10: 0946589089
A much-needed work, which covers all 208 species on the British list. All are illustrated in colour and are given detailed species descriptions in the text.
British Tortricoid Moths, Volumes 1 and 2
Bradley, Tremewan and Smith
Series:  RAY SOCIETY MONOGRAPHS - PISCES CD-BOOK EDITIONS
CD book for Windows and Mac, with fully searchable text and navigation.Pisces Conservation
CD (PC/Mac hybrid) | 2004 |ISBN-10: 1904690122
Two volumes were published by the Ray Society in 1973 and 1979, with over 100 text-figures and 90 colour and monochrome plates illustrating the species, their foodplants and their larval spinnings. While copies of Volume I are still reasonably common, Volume II is extremely scarce, and hence widely sought-after. Pisces Conservation have worked on the books with the kind permission of the Ray Society.
Field Guide to the Dragonflies and Damselflies of Great Britain and Ireland
Steve Brooks with Illustrations by Richard Lewington160 pages, 50 col photos, 235 col illus, b/w illus, maps. British Wildlife Publishing
Softcover | Edition 2 | 2002 | £18.95 | ISBN-10: 0953139905
Describes and illustrates all of Britain's 38 resident and 11 migrant species (2nd edition includes the Small Red-eyed Damselfly and Green Darnier)
The Dragonflies of Europe
RR Askew
308 pages, 29 col plates, 502 figs, 116 maps.Harley Books
Softcover | Edition 2 | 2004 | £30.00 |ISBN-10: 0946589755
First published 15 years ago, this is the only book in English to cover the entire European fauna, comprising 124 species of resident damselfly and dragonfly. All species are illustrated and in most cases both sexes as well as important variants are depicted, all enlarged
Recording advice for Dragonflies at http://www.dragonflysoc.org.uk/
Field Guide to the Bumblebees of Great Britain and Ireland
Oliver E Prys-Jones and Sarah A Corbet
Series: NATURALISTS' HANDBOOKS 6
92 pages, 4 col plates, illus, figs, tabs, distrib maps. Richmond Publishing
Softcover | Edition 2 | 1991 | £9.95 | ISBN-10: 0855462574
The keys are an important feature of the book and are supported by illustrations in colour and black and white, designed to enable the reader to name the British species easily and reliably.
Highland Bumblebees - Distribution, Ecology and Conservation
Murdo Macdonald and Gill Nisbet
53 pages, colour photos, dist maps. Highland Biological Recording Group
Softcover | 2006 | £4.50 | ISBN-10: 0955221102
This book describes the current state of the 16 species of bumblebee found in the Highland region of Scotland. Covers all aspects of the biology and ecology of these valuable insects.
Bumblebees
Mike Edwards and Martin Jenner
108 pages, 90 col photos, maps. Ocelli Limited
Softcover | 2005 | £9.99 | ISBN-10: 0954971302
Photographic field guide bumblebees of Britain and Ireland published in association with English Nature. The guide contains a quick identification chart, photographs of both sexes of all 22 known species
Bumblebees
Ted Benton (New Naturalist Series)
Hbk ISBN 0-00-717450-0 40
Pbk ISBN0-00-717451-9 25
Quick bumblebee ID from http://www.nhm.ac.uk/research-curation/projects/bombus/bumblebeeid.html
Solitary Wasps
PF Yeo and SA Corbet Illustrated by Anthony J Hopkins.
Series: NATURALISTS' HANDBOOKS 3
68 pages, 4 col plates, 4 b/w plates, illus. Richmond Publishing
Hardcover | Edition 2 | 1995 | £15.00 ISBN-10: 0855462965
Softcover | Edition 2 | 1995 | £9.95 | ISBN-10: 0855462957
Revised and updated edition of this classic text, first published in 1983. Keys have been extended to take account of species recently found in Britain for the first time.
Ants
GJ Skinner and GW Allen
Series:  NATURALISTS' HANDBOOKS 24
83 pages, 10 col & b/w plates, figs, tabs. Richmond Publishing
Hardcover | 1996 | £15.00 | ISBN-10: 0855463066
Softcover | 1996 | £9.95 | ISBN-10: 0855463058
An extensive chapter on ant identification forms the bulk of this handbook with keys to worker ants, queen ants and male ants accompanied by colour and b/w plates. A quick-check field key is also included for use in the field.
British Hoverflies
An Illustrated Identification Guide
Alan E Stubbs
469 pages, 12 col plates, b/w illus. British Entomological and Natural History Soc
Hardcover | Edition 2 02 | £37.50 | ISBN-10: 1899935053
New edition of this classic work by Stubbs and Falk. It retains the layout and approach of the original but also includes additional information about the family as a whole, as well as extended and revised species accounts. In all, 276 species are described (compared to 256 in the first edition)
Hoverflies
FS Gilbert
Series:  NATURALISTS' HANDBOOKS 5
96 pages, 68 figs. Richmond Publishing
Hardcover | Edition 2 | 1993 | £15.00 | ISBN-10: 0855462566
Softcover | Edition 2 | 1993 | £9.95 | ISBN-10: 0855462558
A good introduction to these insects with keys to the identification of 42 common species, plus clear and informative notes on biology and behaviour
British Soldierflies and their Allies
Alan Stubbs and Martin Drake
512 pages, col plates, b\w illus. British Entomological and Natural History Soc
Hardcover | 2001 | £39.95 | ISBN-10: 1899935045
Provides a guide to the identification and natural history of 11 families of large and attractive flies that have fascinated entomologists for many years.
Ladybirds
M Majerus and P Kearns
Series:  NATURALISTS' HANDBOOKS 10
116 pages, 4 col plates, 42 figs, line drawings. Richmond Publishing
Softcover | 1989 | £9.95 | ISBN-10: 0855462671
Provides keys for identification and details of the biology of these colourful insects.
Ground Beetles
TG Forsythe
Series:  NATURALISTS' HANDBOOKS 8
95 pages, line illus, figs. Richmond Publishing
Hardcover | Edition 2 | 2000 | £15.00 | ISBN-10: 0855462647
Softcover | Edition 2 | 2000 | £9.95 | ISBN-10: 0855462639
This book contains simplified keys which will allow the identification of the most common, as well as the more localised or rare, species.
Land and WaterBugs of the British Isles
TRE Southwood and Dennis Leston
440 pages, plates, figures.Pisces Conservation CD | 2003 | £22.27 | ISBN-10: 1904690009
Softcover | 2005 | £48.95 | | ISBN-10: 1904690319
Originally published by Frederick Warne in the `Wayside and Woodlands' series, now available again at as a Pisces CD-book, and as a facsimile edition in paperback format. Originally published in 1959, it features 32 coloured plates, 31 black and white plates, and 153 text figures.
Photographic Guide to Shieldbugs and Squashbugs of Great Britain and Ireland
M Edmondson Evans
123 pages, A5 size, col photos.Wild Guide UK
Softcover | 2005 | £17.50 | ISBN-10: 0954950607
The first book to illustrate all of the resident British species in these prominent groups. It includes a colour key with several pages of side by side photographs, quickly narrowing your search to the correct species
Provisional Atlas of the British Aquatic Bugs (Hemiptera, Heteroptera)
Thomas Huxley
118 pages, illus, dist maps.Centre for Ecology and Hydrology
Softcover | 2003 | £8.95 | ISBN-10: 1870393678
Provides illustrations of the eleven families of aquatic bugs and sections on Aquatic bugs and water, Aquatic bugs and flight, food, life cycles, habitats, and scarce and threatened species.
A Pocket Guide to the Grasshoppers, Crickets and Allied Insects of Britain and Ireland
Bryan J Pinchen
108 pages, 77 colour illus, 21 b&w illus. Forficula Books
Softcover | 2006 | £8.50 | ISBN-10: 0954934938
An new illustrated identification guide to the grasshoppers, crickets and allied insects of Britain and Ireland. This book is intended as a quick and easy-to-use identification guide to all 37 native species (grasshoppers, groundhoppers, crickets, buch crickets, earwigs and cockroaches
Plant Galls
Margaret Redfern and RR Askew
Series:  NATURALISTS' HANDBOOKS 17
97 pages, col plates, line figs, keys. Richmond Publishing
Hardcover | 1992 | £15.00 | ISBN-10: 0855462868
Softcover | 1992 | £9.95 | ISBN-10: 085546285X
Covers gall-makers, communities and interactions, identification, keys, food webs and techniques
Collins Field Guide to the Spiders of Britain and Northern Europe
Michael J Roberts
383 pages, 32 col plates, 256 pp line illus. Harper Collins
Hardcover | 1995 | £25.00 | ISBN-10: 0002199815
Major new identification guide to 450 species of spider, designed for easy use without any complicated keys or equipment
Centipedes of the British Isles
Pisces CD-book edition
EH Eason
Series:  PISCES BRITISH NATURAL HISTORY CLASSICS - CD-BOOK EDITIONS
CD book for Windows and Mac, with fully searchable text and navigation.Pisces Conservation
CD | 2003 | £23.44 | ISBN-10: 1904690041
E.H. Eason's work was published in 1964, and has long been out of print. Though some of the nomenclature has since changed, the original species descriptions, illustrations and details of distribution remain invaluable. It is now available again as a Pisces CD-book
Land Snails in the British Isles
Robert Cameron and Gordon Riley
Series:  FIELD STUDIES COUNCIL OCCASIONAL PUBLICATION 79
82 pages, col and b/w illus, tabs. Field Studies Council
Softcover | 2003 | £6.95 | ISBN-10: 1851538909
This publication replaces the single dichotomous key provided in British Land Snails published in 1976 and should enable most beginners to identify all the land snails found in the field in Great Britain.