I was in Windsor Terrace when I was a fresher, and it's really nice, and as everyone has said, so close to uni, and really handy for town, dead close to a metro stop... twas great. I'd recommend that if you want self-catering, but if you want catered then I would recommend Castle Leazes. It's not entirely rich southerners, and it's the biggest of all the halls so there would be a good mix of people. It's not far from uni, nicely laid out etc.
No-one's mentioned St Mary's yet - it's also quite a way out, but it's not an unreasonable walk to uni. It's self-catering and it's really nice, and although probably a lot calmer than the others, everyone there seemed genuinely really nice, decent people. Also pretty handy for Morrisons.