The place I stayed at was £125 per week, breakfast included and evening meals were extra but well worth it - its nice to come home after studying and not having to worry about finding something to eat! There are lots of good places to stay on the accomodation list on the BGS site.
My exams were at gatwick - managed to get a couple of nights at a saver rate which you can get off the website, £26 per night which was handy!