Maths A Level overall grade issues

This year has been a little messed up. Last year, we sat P1, S1 & D&D1 modules, in which I achieved A grades.

This year, the teachers decided to opt for moving from the Pure modules to Core modules, meaning I had to scrap my P1 score, and almost do a resit with C1/2.

This year, we have been made to sit papers C1-4. In January I sat C1 & 2 and results were fine, but to be quite honest, I don't think we've allowed enough time to do all the C3 & C4 work, and so I am struggling.

The C3 paper is in a weeks time, and there is no way I can do enough preparation for it. However, I NEED an A in maths overall for the course I wish to do at Uni.

To help put my mind at rest, what grades, roughly, would I require from papers C3 & 4, based on the fact that I currently have As in the other 4 modules I have sat? Do C3&4 account for more of the overall grade, or is their importance equal to that of the D&D1, S1 and C1&2 papers I have sat already?

I think I got around high 80s and low 90s for the Core papers I have sat so far, about 90 for Stats, and 100 in the D&D paper if this helps making any judgement. I can't seem to find how much each paper is worth.

In other subjects, I have been told I need like a B & C in the papers coming up to secure an A overall. Will this apply to Maths too?

Thanks for the comments everyone.
DOJO, I am with OCR.

I have done some of the Specimen papers released though, and I find them extremely difficult, which is why I am quite worried.

The first c3/c4 papers are being sat this summer so the board wont make them particularly difficult. I imagine the upcoming January exams will be tough for the core modules.