I am an ex BGS student and I would agree with what has already been said. I cannot compare OAT set up as I never went there (or considered them), however I can say with BGS that I achieved 1st time passes in all exams (thereby keeping the cost minimal) I can, through experience, say that BGS has a very experienced group of instructors who know how to cram in all the necessary information regardless of your background, experience etc. I have recommended Bristol to a number of my friends and colleagues and those who have taken up the advice have similarly strong feelings about the flawless standard of instruction they received. As was said before though, not worth getting into a war over it as no-one (apart from your bank manager) gives a flying one when it comes to the bit.
Best of luck wherever you go!
Alex, do the very lovely maidens 'still' have very useful sewing equipment? And has Baz still got his annoyingly oversized (piece of) CR*P - at least is that still what he tells all the ladies!