I agree after reading all the posts that you did the right thing. Really what is the difference in you picking her up, and taking her home to re-home her with somebody who cares and the animal welfare doing it? It's just that animal welfare do it 'officially'. He doesn't sound like he cares about these cats and if they're out all day and night and not fed very well then I see no reason why somebody else can't have her.
I think you should do the hypothetical thing and ask him the next time you see him, perhaps say a friend saw the cat and thought she was lovely and said they'd love a cat like that and see what his reaction is...if he's not bothered and is disinterested then I think that's a green light to go ahead.
Then tell your friend you've cleared it with him, and then she'll have a home.

If not try and find somebody else who'll take her she's lovely.