Maths is good. Can you take up Computing? If not, can you take up Further Maths? If not can you take up physics? If not can you take up another STEM subject?
My brother is doing computer science & he has A levels in Maths, Further Maths & Physics. He got accepted at all 5 unis he applied for, as far as I know, so I guess those are good for computer science. If you can switch to one of those (if you're finishing y12, they might let you do an extra AS in y13) then that might be an idea!