How good are your notes for History? For that one, if you have notes that cover everything - and by notes I refer to teacher notes as student notes are hardly ever adequate enough - then you'll find it easy enough to get a high mark. Just memorise all your notes and cram it in.
For maths - that one depends more on how good you are at the moment. You'll probably get similar to what you were working at currently, usually with good revision half a grade to a grade higher than that. The best revision I found for it is the CGP revision book- I went over everything in the book and made sure I understood it, and the exam was easy.