Congratulations on those excellent results.
It's good to see you trying to make an effort to speak to people in the industry.
I would suggest you take whatever a-levels you feel you will achieve the best grades in, which, seemingly for you seems to be maths and science so I would suggest they are solid choices.
Yes those grades are above and beyond what's required. From my experience most airline cadet programmes just want you to meet the minimum standard, above that they aren't really interested. What's far more important are your interpersonal skills e.g. can you work well in a team?