Another update. We didn't rehome him, I couldn't bring myself to do it, especially after thinking some more about Gwen's post.
He'd been missing for two months, and although our old neighbours were seeing him around occasionally, none of them were able to catch him for us. At long last, we had a call yesterday to say that they'd got him. He is definitely being fed by someone - his lean, hunter's physique is gone, he weighs a ton and, apart from his face, looks like a proper domestic cat. No fleas (normally he's covered when we collect him after an absence).
So, he's back here at the moment, going in to kennels tomorrow because we're away for the weekend.
We've just bought a big collar tag from Pests at Home that says 'Please Don't Feed Me!' very clearly on the front, with his name and telephone number on the back - hoping that this will be more obvious than the little barrel tag he had before. No-one knows who is feeding him, although I have a suspicion that it's the lady who bought our house from us, she won't answer the door or telephone to me though
I had thought that maybe the kindest thing was to try to get her to adopt him.
Failing that, we're going back to square one and will pretend we've just moved. He is living in one room at the moment, and only being let out in to the rest of the house in the evening. I'm hoping if we can keep it up long enough, and make home an attractive enough place, we might have some success.
If any new forum members have any bright ideas, I'd be happy to read them!
"Happiness is like a butterfly; the more you chase it, the more it will elude you, but if you turn your attention to other things, it will come and sit softly on your shoulder..." Thoreau.