For the exams: GCSE maths and physics/double science would be good, at a decent grade, but by no means essential. Have had good students who left school 20-odd years ago with no qualifications or ahandful of O-levels or CSEs. One student I knew with good results in ATPLs struggled with GCSE Maths and Physics on the resits! Didn't stop him getting first-time passes, even in Nav, the most mathematical subject (although that could be down to my instruction
).
Even for sponsorship I doubt an A would help more than a B, unless you are competing with a condidate of almost identical regard from the interviewers!
i.e. Don't worry!