What A Level for aerospace engineering?

Computer science is probably going to be more useful!

Both are potentially useful in their own way. Some topics in aerospace you may find some chemistry background useful for (thermodynamics, materials, possibly stuff to do with chemical propulsion) while CS (or more specifically, having some programming experience) is in general useful for engineering. It should be noted all will be taught from scratch assuming no background in either area though. I might note however, it's much easier to develop some programming skills in an extracurricular fashion, and a lot of relevant extracurricular activities you could undertake that would also be relevant for an aerospace application (e.g. robotics anything) than learning chemistry material independently.

Hi!
I know for certain that I’ll be taking physics, maths and further maths, but I’m stuck deciding between chemistry or computer science. Do you guys have any opinions or help?
Thanks

Chemistry might be a tad more useful for certain elements of the course as @artful_lounger says, but I doubt it'll make much difference. In maths - with the additional of further maths - you've got the main subjects. I usually just advise people to take whatever subject they'd prefer to study and achieve the highest grade in.

Hi!
I know for certain that I’ll be taking physics, maths and further maths, but I’m stuck deciding between chemistry or computer science. Do you guys have any opinions or help?
Thanks

Computer science but I took chemistry, it did not hinder me in any way tho.