My son is now a quant trader in London after having read Maths & CS at Oxford. The well known firms (Citadel, Jane Street, Two Sigma, SIG, DRW, Five Rings) focus their recruiting on the Math/CS students. Here’s a link to last year’s career fair booklet.
https://www.careers.ox.ac.uk/files/jobs-maths-fair-booklet-2022pdf
A maths offer will be very difficult for you to achieve with the 4 in Calc BC. You would likely need fives in Physics C and CS A to meet the “relevant subjects” criteria for your APs and a very competitive MAT score in the fall to get shortlisted for interview. The fact that your Physics C scores will be predicted (since you are taking it senior year) won’t be helpful either.
There is a new undergraduate program at Imperial that is a combo of Economics, Finance and Data Science that might be worth a look.