Take a look at the Natural England website www.naturalengland.org.uk . It has lots of information about wildlife gardening and some very useful tips and hints. The following is certainly good advice:
Relax! Don’t feel that you have to be too tidy in the garden. Leave some areas undisturbed, especially between March and May. Piles of leaves and twiggy debris in a hedge bottom, or out-of-the-way corner, will shelter frogs, mice and hedgehogs, and the seeds in dead flower heads can be valuable food. Let a patch of grass grow longer, as this encourages wild flowers, provides shelter for small mammals and food for some butterfly caterpillars.