1. The sort of people that go to york university (quite alot of public school/ state school in comparison to Exeter, durham and Leeds?) Few Public school people, though I do know a few. Not noticably "rah" though.
2. What the course is like A friend of mine did economics and really enjoyed it - can't say first hand
3. Accomadation (i.e do you choose a college or are you place in it and what are the rooms like) You don't choose a college, though you can express a preference. This is rarely listened to, but worth a shot. Rooms vary wildly based on which college (and how much you're paying), but all are decent serviceable rooms. Just don't expect perfection from anywhere, these are student rooms after all.
4. Social life Varied; some clubbing but mostly pubbing. No central SU, but lots of campus bars. Look on other threads in the York forum.
5. CampusConcrete, lake and ducks. I love it. You may not. If you haven't already, it's worth visiting; the atmosphere is not something that can be described. Oh, and everywhere's close together, so it doesn't take long to walk across campus.
Hope that helped.