Well if you're resitting F321 and F322, and you've yet to do A2 even without including the UMS from your ISA you'd have a maximum of 540 UMS to gain which would be an A*, not saying this is likely but you're practically doing 2 years of A Level in one year, the ISA you have from last year is almost insignificant relative to the rest.
Now, if you include the ISA, which I am not sure how many UMS you received but the minimum is 36 for a C, meaning your maximum total UMS would be 564.
A B overall would be 420 UMS, meaning you'd need a total of 384 UMS in A2 and your resits.