You are going to get yourself in a mess if you base your academic future on what mates have said, or even on what you read here - unless you weight the opinions that you listen to according to the qualifications of those that hold them. That's a hint, Johnny. Check my profile and investigate some of the advice I've given to others. I am not a wet-behind-the-ears Wannabe; I am an airline pilot with over 12,000 hours and an abiding interest in trying to ensure that would-be pilots get good advice. I've been in the flying business for 27 years, and in training and recruiting (for the RAF) for a good proportion of that.
Now, if you are intent on getting a sponsorship to fly for an airline, you are going to have to study the requirements of those airlines and organisations that offer sponsorships. In the last year that has included Britannia, FlyBe, and easyJet (through CTC). There have been very limited part-sponsorships from other airlines, but they are fairly insignificant in the scheme of things. British Airways, whatever you have heard elsewhere, are not operating any kind of sponsorship scheme and have not done so since early 2002.
Go and check the web sites of these organisations and find out the required qualifications for yourself. If it really interests you, go and look at other, non-sponsoring, airlines and see if they define any kind of academic qualifications at all for direct-entrant pilots - you'll find that the vast majority don't.
It seems to me that you are not confident that you have the interest or ability to pass Maths at A2, or an engineering subject at degree level. Only you can answer this truthfully, but you will be wasting your time (and possibly your parents' money) if you embark on a course that you are destined to fail - and you will get no credit for that from anyone. Pilots with engineering degrees are no more or less valuable to an airline than pilots with music degrees - you will never be asked to use the skills of either discipline whilst flying your aeroplane. Please do not counter that 'it's obvious' that engineering degrees count for more - they don't. Believe me and move on.
If you wish to study aviation engineering because the engineering of aircraft structures and so on is your abiding interest, go and do it - and enjoy it. But I'd have to ask why you wanted to become a pilot if engineering is your passion? Equally, if you are passionate, knowledgeable and confident in, say, music technology, why not do a degree in that? The 2:1 you'll get in that standing on your head is far more useful than a fail in an aviation-related subject. You ask about other aviation subjects; well, there are a few courses in airline management and operations (see other threads in the Wannabes forums), and I'm sure they're good courses - though some are professional-enhancement products aimed at people already in airline ops and management. Get some information about them, and, if you feel that you can make a good job of one of them, give it a go. The course literature will tell you what the university believes are appropriate A-levels for these courses, which will help you decide which A-levels to take. These courses may make you marginally more attractive to some employers, but most won't be that fussed. It's a degree, which is very nice, but they're employing you as a pilot, not an airline manager. On the other hand, one of these degrees may be the second string to your bow that we try to advise Wannabes to have....
Is there a bottom line? Not really. You must carefully research the routes you could take to getting into flying. There are quite a few, and their academic requirements will be significantly different. Once you have a firm grasp of the facts obtainable by careful study of university and airline websites, you will have a clearer idea of wht may be required of you. Above all, do not base any career-influencing decisions on the opinions of mates or anyone else who hasn't been there, seen it, and got several of the T-shirts.
Scroggs