There are a great many groups working with British wildlife, we have supported the work of the Wildlife Veterinary investigation Centre in looking at causes of death in wildlife. The work of this lab has contributed a vast amount to our knowledge of what is happening out there.
The work of the Wildlife Trusts is vital across the country, our Managing Director worked with the Hampshire Wildlife Trust on otter release, and this project has succeeded well. Vetark are corporate members.
We also support various bat rescue groups, these fascinating animals aren't 'sexy' in the same way that hedgehogs and rabbits are to get sympathy, but they are very important as environmental 'health' indicators.
JNCC have developed an excellent document regarding supplementary feeding of squirrels (don't put out food if both reds and greys are present!). The link is below.