Self Teaching Further Maths.

Taught myself AS fm this year (FP1, D1 & D2) in basically no time at all and with no difficulty. Now wishing I had been brave enough to do the whole A level, I thought self-teaching would be a lot harder than it has been. I found that FP1 is a lot easier than C3 and C4, although neither of those are particularly hard tbh. Can't speak for Mechanics as I did stats instead.

The specification says that C1 & C2 knowledge is needed, but some people say that doing C3 & C4 is necessary.

I was not allowed to do further maths at my school, so i am deciding to self teach it. I am going to teach myself C3, C4, FP1, M1, (Maybe M2), FP2, FP3, D1 & (Maybe D2 )(in that particular order). From summer till late december i will teach myself C3, C4, FP1, M1 & M2 (Maybe FP2 depends how formidable i may turn out to be in C3, C4 & FP1). I aim to complete all those six modules in the summer & use my September to December period to recap on them. After january exams i will complete the rest (Not sure about D2 does it add any relevant knowledge that could help me? if i were considering a course in computer science?). Are all these modules particularly difficult to understand? Which ones are relatively easy and difficult? Which ones could i complete the fastest?

At the moment i am getting 68/75 in C1 & 71/75 in C2.