I'm studying for the MCAT right now
I came from a British school system and the science content in the MCAT is basically like A levels but a bit more advanced. I got credits from my A levels for 1st year sciences so the bio, chem and phys will definitely help no doubt. The math doesn't really matter, it's not a big part of the MCAT, you just need to know basic math that helps with physics questions. But just remember that the way the questions are asked in the MCAT are not like what the tests would be for these courses, it's much much much more application based.
You should buy prep books though with the whole review of what you need to know. I'm using Princeton and EK books so when you buy them, they'll be enough practice for you too!
Hope that helped.