It sounds like curds to me, Abi. Does it seem to get less between feeds? Curds are like a coating, and quite thin, whereas thrush can be quite cottage cheesey. And it may bleed when it was rubbed if it was thrush. If he's had it a long time, he would probably have patches on the roof of his mouth, inner cheeks and gums too. This page shows a picture and the breastfeeding network is really helpful about such stuff too. It's really difficult to keep their tongues milk free, especially if they're feeding 3 hourly. It really bothered me that it might be thrush with Missmarbles but our HV (who is really sensible and fab) said it was just curds and not to worry too much. I told her I couldn't get it cleared, as she was feeding and sometimes still does about 2 to 3 hourly at the time. Eventually it just went.
Susie I hope they get your brother's sugar under control soon and he gets on the mend. Scary times.
Mmmm weetabix brownies, may have to investigate that further, Brain 
Aw Amey, it's horrible when they're poorly
I hope he's ok and you both get a good night's sleep, and that he will feel better in the morning.
Sorry for hopeless DH's, Small. I don't think men do get it, and how they manage to conclude they are more tired is incredible I think carrying and bearing the baby, which takes it out of you, and then you don't really recover properly before you start the sleepless nights; it's eshausting, but I don't know a single couple who doesn't have this tiredness competition at some point when their children are little.