You’ll most likely struggle at Alevel if you only do foundation level maths. You need to ask your college/sixth form what GCSE requirements for your subjects are and if they’re are nice they might enrol you into the course and let you take GCSE maths higher in Y12. Realistically you don’t see people who sat GCSE foundation maths take on that many science A-levels because there are some maths heavy topics. If you’re really wanting that 6 and move into higher maths, it all just depends on your work ethics and how much you actually want that 6. A 6 in GCSE maths isn’t that hard for the majority