Erm... there were definitely some public/private-school oddities when I went for interview, but everyone I spoke to was lovely, to be honest. Yeah, the girl I shared a room with spent most of the time on her phone checking up on her horses and complaining that she was missing the lacrosse season, but we stayed up chatting for a while and she wasn't a snob at all.
In fact, my inverse snobbery was probably worse... felt quite ashamed afterwards... it could have been that you were a little hyper-aware of your state-schoolness when you were at the conference. I know I've always felt a tad self-conscious when I've gone down, and taken offence at things I needn't have. Besides, I have it on pretty good authority that the real snobs tend to retreat into their own little world and get ignored by everyone else, so we should be fine, lol.