But he doesn't get the particular speech patterns. And, at the risk of offending certain participants in this discussion, he's always seemed more American than anything else to me.

Don't you mean Dean Thomas, then? There is plenty of variation in the social background of Rowling's characters, but that makes it all the stranger perhaps that only a few characters get the speech patterns to go along with it.

And Dark Knight's point was indeed also part of what I meant - that the wizarding world as depicted in the books is largely middle class. They have to have a constant inflow of Muggles, some of those working class, but it seems to me like Hogwarts graduates such as Dean and Colin, like Snape in his time, would still mostly end up being middle class themselves in the wizarding world even if they're from working class backgrounds in the Muggle world.