I was at Center Parc in Elveden Forest this week for a Workshop, and saw no end of squirrels and small deer. I'm not sure what the deer species was, they were a lot smaller than the larger deer you see wandering around places like Richmond Park, probably only about the size of a medium sized dog. I'll post a photo next week, since I've just had to power the server down for the weekend (electrical safety testing).
The squirrels are incredibly tame and cheeky, checking around the chalets for anything they can find to eat. You come across them all the time when walking around the site, but on a bike you catch them even more unaware. The entire site must have tens of thousands of them at least.