Pre university education

I’m currently at Bath uni (meant to be a decent semi target for those who don’t know), and I’m doing STEM. However my alevel grades are AABB (+A in as further maths, if that even matters). Should I retake some of these despite having already finished 1st year (I didn’t do well, but I’m planning on working hard in second year), or is it pointless (even if my grades become AAAB)? Other options (though probably stupid) could be to take the sat and get a 1500 plus score, would that be beneficial? Current plan is to do a target masters after uni in finance as I wasted first year.

Please tell me your opinions and offer advice on what to do in my situation.

Thank you very much.