Rescue centre who will do a home check. So many fraudsters out there pretending to offer caring homes who use them for dog baiting. Hounslow Animal Welfare, Mayhew, Cats Protection, Celia Hammond Trust, Blue Cross, Wood Green, RSPCA (apparently Southall branch is good but be careful of other branches as they are pretty free with their lethal injections if a cat isn't rehomed within a week and if it has any health problems, it's a gonner). Google local rescue centres for a more complete list but those would be a good start. Bear in mind that even no-kill rescue centres will often kill an animal that has fiv or felv - there is actually no need for this, they just need to be indoor only, ideally solitary cats.
Claire Moran ● 2257d