My cousin's a third year at Wadham, doing the 4 year MPhys. From what I remember you can choose from different price brackets - I could be wrong though! She chose the cheapest option. Her first year room was quite small, but had a sink and possibly a fridge (can't remember the finer details of it anymore). However, it was like a furnace all the time - she always had her window wide open, even in early November when I visited her, but it made practically no difference to the temperature. This year it seems like history is repeating itself, as her room is above the boiler!
She had to move into private accomodation in her second year with several other people she met at college, and in the third year rooms are allocated by ballot, so it's the luck of the drwa what you get. In the fourth year she's moving out again, this time to college-owned accomodation in Summertown - probably the Merifield housing mentioned above.