Regarding the A-level History comments..
I found AS-level History more difficult than A2, I think this is because one of the modules covered several periods in German history [right from before Bismarck through to the rise of Hitler] whereas at A2 the Germany module we did was purely on the Nazi state, it was more focused. Despite History being a huge leap I didn't find it particularly difficult, I got an A anyway.
History at A-level is one of those subjects that requires you to really think. If you listen properly in class and read widely and think about the issues then you'll do well, but it's harder than GCSE in the sense that it's much more than just remembering a few facts and dates [which GCSE was].