No problem. Do watch out for calculus, though. If you want any hope of understanding it, you'll need to go outside the syllabus. Especially for definite integration. A Levels teach definite integration as a method of finding the area under a curve, but tells you nothing about how we arrived at this process. For that, you'll need to know differentiation from first principles, Riemann sums, the squeeze theorem, the mean value theorem, and the fundamental theorem of calculus, respectively.
Without this understanding, definite integration will just seem like some sort of magic formula to find the area under a curve.