i really wouldn't worry about general studies. i got an A for my AS and did no revision what so ever. the main thing is that you write clearly and put your arguments across in a legitimate way. as for the science/maths paper, that's just a joke, i hadnt done a science or maths subject for 2 years yet got full UMS marks (please don't think i'm bragging, i'm by no means overly intelligent i'm just trying to show how easy it really is), the whole paper was just basically common sense.