MEI AS resits not covered in A2Watch
What topics from C1 and C2 would you recommend revising which aren't covered in C3/4.
Sequences and series (arithmetic, geometric, term to term)
Use of the discriminant to solve problems with roots
Radian measure for sector arc length and area, area of a triangle, sine rule and cosine rule.
Maybe some area, surface area, perimeter, circumference, volume refresh for applications of differentiation question if you feel you need it.
I've moved this to the Maths SH section where you should hopefully get some more replies.