If your unsure about you knowlage of maths, i would suggest takeing a refresher course at a flight school, e.g Oxford Aviation Training (OAT). The advantage of doing it at a Flight School is that they know from experiance what type of subjects within maths to cover extensivly, as they know whats required on the ATPL exams...
Or if you like, OAT kindly offer a cd-rom course. I have the Essential Maths and physics and i personally find these very helpful and easy to understand. I believe these are around £30.
Hope this helps and all the best!
Jay
