Another vote for Andrewsfield. I did the CRI course with Bob last year, with Carol as the examiner. She can play the part of a numpty student perfectly!
Another advantage of Andrewsfield is that they have a caravan you can use which will save you loads on accommodation costs. I stayed in a Travelodge in great Dunmow (about 3 miles from the field) and got a good rate (about £30 a night I think) by booking well in advance but it would have still worked out pretty costly for a full FI course.