If you have a choice of venue, then Silsoe is one to be considered.
Accomodation is around the 30quid mark for a room in the Conference Center which about a minutes walk from the exam hall. Rooms are all spotless, quiet and comfortable. Breakfast is included which you get from the main dining room in the college, a good hefty fried breakfast is available.
Dinner can be had at thestudents union bar for under a fiver.