Hi pchome -
I can recommend Ceilia Hammond, they're just down the road in Lewisham Way. http://www.celiahammond.org/ (you can browse through some of their cats that need re-homing on the website)

I got my cat from there and have absolutely never regretted it. They also regularly have kittens and young cats, during kitten season and beyond, and often run out of space because so many stray or unwanted mums with litters are brought it and taken care of or fostered. It's quite heartbreaking, so would be great if you could give one of their cats or kittens a home!