A2 maths exam advice :)

Retake c2 and possibly s1 with c1. Just get as high as you can in the As units and still aim for 80+ in the A2 units.

D1 is a easy as it gets, so you should manage high 80's or higher. I would recommend resitting C1. plenty of people I know did poorly 1st time round, and got much better scores the next time round. It shouldn't need much revision, as you've done much harder stuff.

I think you should definitely retake C1 to maximise your chances of getting your A. It shouldn't really add much pressure since you've done C2 and C3 - etting good grades on both. I would also consider resitting C3 or C2 but it is by no means necessary. Good luck.

I'm in practically the same position as you, apart from i've done C1-3 and D1, with M1 this year.

C1 - 86
C2 - 81
C3 - 80
D1 - 71

I'm going for a D1 resit although my tutors argued that it's something too different (ie. i've never done D1 since so my skills aren't sharp) and suggested C2 instead. Certainly doing an AS core module would be easier - either C1 or C2 in your case. You do build on the core skills, have a look at the content of each and which you prefer. Doing 10 past papers in the week before is probably enough to bump it up a little. My expectation is that i'm probably not going to do any better in C4 than I did in C3 so I wanted a safety (and I suspect similarly for you there). D1 was quite an 'easy' module but everybody seemed to do much worse in the actual exam. Just seems a funny one! How do you feel about the content right now?

What's the offers you need to meet? Can you get the A in another subject instead or does it HAVE to be?

tlr;dr: I'd recommend sitting C1 or C2 again, possibly both if you can be bothered.