It's one big lump, so I dunno about thrush. No sign of spreading.

Hadn't thought of hand, foot & mouth. He has had that before though...(but they weren't 100% sure on diagnosis cause the bumps he had weren't quite typical).
Well, mum had the bright idea of calling our Child health nurse - d'uh. don't know why i didn't think of that. So i'll see if she has a minute tomorrow. The clinic is a short walk from here, so we might get lucky.

Thanks for the replies!