No its not easy, if for no other reason than the vasts amounts of information you are required to retain.
However if you are getting 70% average prior to a brush up at Bristol then you will have no problem.
The 2 weeks at the school are very very good and I would go so far to say that you don't require that greater understanding of the subjects prior to the course. The team at Bristol really will give you what you need.
Best thing you can do is go over anything that you think is a bit of a pig and get the questions in your head that you need to have resolved when you get there.
Dont be under any illusion though the course will be sleep and study , dont take a book or beer money !
good luck with the exams youl be fine im sure.
Flyfish