You seemed to have your head screwed on for a 17 year old. I think it’s also good how you haven’t fallen for marketing and glossy brochures from prospective flight training organisations
Firstly I also agree with both mad_jock and G-FORC3 about getting the class one before you do anything else.
Keep working hard at those a-levels. You’ll need BBC or better to be considered by BA through the FPP.
Future Pilot Programme - Future Pilot - Share your passion Best of luck with the PPL also.
In terms of what else you can do, I would suggest trying to broaden your CV as much as you can. Get involved in as many extra curricular activities as you can. Volunteer to take roles that involve leading teams and working as part of a team. Interviews are often competency based and will ask for examples of things you have done in the past that demonstrate the qualities that this particular airline/job wishes you possess. Whilst doing my a-levels I found it helpful to start a word document. I started out by listing all the qualities that potential employers look for in their pilots, and then I thought of times when I had demonstrated these qualities. I aimed to get involved in more activities to have a better range of topics available to discuss at interviews.
It worked for me and I made it onto an airline programme.
Best of luck