I agree with Bunsey I would also go for the most "un wanted" and "un loved" one possible, even if it means waiting for a bit one will invariably come up, they always do - especially at this time of year when people are going away on holiday and can't be bothered to find someone to look after their pets
I do wish I'd known you were looking, I was in Suffolk on Saturday and I have a little 5 week old rescue girlie here who will go to the Pets At Home Adoption centre, I could have bought her for you
how annoying!
You can also try this site
http://www.pet-rescue.org.uk/ click on HOMES NEEDED