Just to see where I was at, I decided to complete a past paper. I scored 38/60 on the June 2014 paper, which isn't the best but was sufficient for an A grade that year.
Should I just revise the areas where I didn't scoop up any marks?
Always revise! Go through and analyse the past paper, see where you went wrong. Always, where did you do the past paper? In exam conditions at school (in the hall) or at home? It seems that the paper is always harder when you are in the hall for a mock...