Retaking 3 AS in Oct/Nov alongside A2?

im not too sure how your school/centre is doing it. But there is no need to do AS-levels since 100% of the grade comes from the A2 Level exams. So personally its pointless to focus on AS since there might be small differences in how the content is covered (which will result in confusion when doing the exams for A2)

I did A-level Bio, Chemistry and geography. so i dont know if your subjects are different. But i would recommend focusing on the A2 exams

For my school, 40% is taken from my AS exams and 60% from the A2 exams sadly.

oh snap... do you live in wales or N.ireland cuz i just googled it, and yep its 40%.

well then if i were you i would do both AS and A2. just make sure you know distinctions between the content. e.i. if The heart is assessed in little detail in AS but in big detail in A2, you know that when answering a question in AS you don't over explain or you may waste time and miss what the question is trying to ask you.