As Poppy9560 says, please phone Celia Hammond Animal Trust in Lewisham (020 8694 6545 - you might need to leave a message on the answerphone).

If they are feral tomcats they might be be trapped, neutered and then returned to the area - it is kitten season at present and the shelter is full to bursting with mums and kittens so they might not be able to take in male cats for rehoming. But just getting them neutered will help to stop more feral kittens being born, as well as their own behavioural issues (fighting, pestering pet cats, spraying etc).

Good luck!