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Just quoting in Puddles the Monkey so she can move the thread if needed
Can I drop C12 after As? ( I cash-in-coded that subject) and later do a foundation course for Maths?
To get an AS you need to have taken C12 plus another unit - e.g. S1 or M1. You can stop at this point with an AS (or stop with only C12 and get nothing from it).