Collins Complete British Animals Compact and useful, this combines clear photos with informative text. At the back there is a good little section on skulls and droppings too.
Mammals of Britain and Europe (Collins Field Guide) Comprehensive, detailed, with clear illustrations. An essential field guide for those interested in European mammals. Not always easy to get hold of though.
Deer Watch: A Field Guide For anyone with an interest in the deer that inhabit the British countryside, this wonderful book is a mine of information.
Animal Tracks and Signs (Pocket Nature Guide S.) 'Preben & Preben' is the benchmark book for the identification and interpretation of the tracks and sign of European animals.
Tracks and Signs of the Birds of Britain and Europe (Helm Identification Guides) Very thorough and detailed. Includes tracks, droppings and feeding sign but especially good for identifying feathers and skulls.
Collins Field Guide - Bird Nests, Eggs and Nestlings of Britain and Europe Quite specialised but this sometimes hard-to-find guide fills in gaps not covered in the Helm guide, especially eggs.
Collins Bird Guide Well laid out with very clear illustrations. My favourite field guide for birds.
Collins Bird Songs and Calls (Book & 3 CDs) Many people struggle with identifying and differentiating between the sounds of different birds. This 3xCD and book combination provides a solid grounding.