I've been compiling revision notes since the end of February, and started doing just general revision at about twenty minutes/half an hour a day on top of my usual college work around mid-March. Started 'hardcore' revision on Sunday, although I haven't stuck to my timetable as much as I would have liked so far (supposed to be doing about eight hours a day, most I've done is five).
I've gone through three sections of Chemistry so far - Kinetics, Energetics and Equilibria, about two sections of Biology - Genetic Variation, DNA and a bit of exchange, and only covered Matter and Radiation for Physics (and I have to do both the Unit 1 and Unit 2 tests this summer!). Haven't done anything for Critical Thinking (not a priority), and wish I'd done more for English Lit, so far I've just compiled notes for about half a dozen poems and one and a half scenes of the play.