The Cats Protection League are usually more helpful - if you can get a local phone number, a real cat lover may come out and be willing to take them in. The RSPCA are usually hopeless, from what I've heard. At least with dogs, you can usually get the police to take them, I'm not sure about cats.
I went for them purely because we knew where the outgoing tenants went and I wanted them to go for a prosecution. Fortunately, one of my colleagues used to be an Animal Warden, and had the numbers of several RSPCA officers on her mobile. She called one of them and briefed him; he straight away got onto the outgoing tenants at their new address and got them to pick up the cats there and then in his prescence. Just goes to show it's not what you know, but who!
Cross posting I take part in a couple of quizzes on-line and have created a testing ground group on MSN. If you like this one I will do another longer one next week. There are only two rules 1. only one answer per posting 2. no consecutive posting.