Hiya, I’m in yr 13 now and I’ve been doing lots of research into universities, I think I may be able to offer some insight into what I’ve found out!! Maths is definitely a great one to go for, especially if you are thinking about engineering. Lots of engineering courses require maths but even if you don’t end up going down that route, maths is usually considered a very good a-level to have! I would definitely recommend looking into some of the courses you’ve been thinking of taking at uni (though it looks like you’ve already done this!). Engineering may also want a science-based subject as well as maths so physics would be good in that case but it depends which unis you look at! A heads up for physics though, it is a tough subject so you do have to really want to do it, if you’re willing to put in the work though it is a great subject.
Whichever a-levels you chose though, my best advice is to make sure you have looked at everything you do in that course. Don’t pick an a-level because you like one topic but at the same time, don’t be put off of an a-level because of one topic. It’s so important to know what you’re getting yourself in for, speaking from personal experience (I chose physics for the astrophysics topic and ended up missing the whole topic due to a medical issue!!).
Also, remember, it’s better to pass (and pass well) on a subject less related to your future job ideas than to fail (or not do as well at) one that’s more related. So when choosing, consider whether you think you can pass with the grades universities ask for!
If you have any other questions I can try and answer them for you - for reference, I do maths, computer science and physics a-levels! Best of luck making your choices, I’m sure you’ll make the right ones and remember, there are always other routes you can take so try not to stress too much about uni