Cheers BOF, belt ordered for tomorrow and an alternator too. How difficult is an alternator and belt change on your drive? Is it an easy job or does half the engine have to come out to get access to it?
I don't know how we got from 'maybe the belt is greasy or loose' to 'I'm going to change both the alternator and belt' in one easy jump, without even checking the belt condition or tension. And, anyway, the tensioner could be the problem.