Only you can say whether the degree is suitable for yourself: I cannot stress enough that it is
far far better to do a degree which you enjoy/will succeed at (and the two are linked) than to choose one you think "aviation companies" will prefer.
By all means if you enjoy Aero Eng/Management then great, go for it.
So, in my experience airlines do not really care what degree you have, or even necessarily if you have one at all. It's more important to demonstrate that you
can study, learn and self-motivate. That can be demonstrated by academic success (in any field) or by other extra-curricular means (or even better, both).
If your goal is the Royal Navy, bear in mind that they certainly won't care that you do an aero-related degree, unless you are thinking about AEO, although I suppose it would be an indication of your level of interest in flying. Not a reason in itself to go through 3/4 years of torture doing something you didn't enjoy, though.
They also will not want to hear that you are thinking (if you are) of using the RN as a flying training organisation. Of course it's sensible to have a Plan B, and to give yourself options, but you don't have to tell them that. It's career folk they want!
PS: I did 5 A-levels (inc Gen Studies; come on - we know it's not a real A-level!
), did some work experience within aviation, had a PPL at 18 and did Aero Eng at University. Spooky, eh?
However I prefer girls, so applied for the RAF instead.