Tiram,
Sound advice from above, and with most people it is human nature to worry about the unknown.
I wouldnt get too bogged down in trying to obtain every source of feedback and spending hundreds of pounds doing so. When I did my exams, I found feedback to be a handy tool to highlight the areas I was weak on. What ever you do don't learn feedback, you will most likely come unstuck.
As has already been said, work hard, try to understand the subject the best you can and take the exam, you will most likely do alot better than you think. I remember when I did my first set, I thought I had failed them all, and two weeks later when the CAA A4 envelope popped through the door I had a smile on my face from ear to ear
, all the hard work had paid off.
Work your nuts off, and you will reap the rewards, good luck, and try not too worry!