There are loads of posh people in the sense of went to private schools and come from very middle class families with parents paying for their fees and/or accommodation, so my comprehensive school, working class, first in my family to go to uni background sticks out a bit sometimes, but I haven't met any posh people in the sense of being snobs. I've made some really good friends here who'd I'd class as 'posh'. Everyone is down to earth and friendly and no one looks down on anyone else for the way the dress or what car they drive, so it's really not an issue unless you choose to make it one. As for black people, there are very few of them in Exeter generally and even fewer in the uni itself, but again it's not an issue unless you make it one because I haven't seen/heard about any incidents of racism here.