Does this sound like a good A-Level Combination?

Chemistry would complement Biology, Maths, and Physics well, but do YOU want to do it? If you're no great fan of Chemistry (look at the specification online or ask your teacher if you can flick through a textbook), don't take it - you'll need to put double the work in to do well.

It's impossible to know what you want to do with your life at 15/16. Heck, it's nigh-on impossible to know what you want to do with your life at 40. Focus first and foremost on the next couple of years and what it will be like to study during them, and then glance to your 10-year future, not the other way around. If your subject choices are ones that you enjoy and/or want to study, the rest will come much more naturally.

i would do chemistry, but unfortunately i didn’t take it at GCSE and i really really doubt the teacher at my school would allow me to do A-Level without GCSE

I assume therefore that you took the 'Double Science' GCSE? If so you should be set-up to take A-Level Chemistry (same as Biology/Physics?)

I live in Northern Ireland, and at my school you either did single award, or else you could pick whichever individual sciences you want, and i chose to do Biology and Physics but dropped chemistry 2 years ago

Ahh that makes sense - so have you not done any Chemistry beyond Y9 (or the Northern Irish equivalent if there's a difference)?

unfortunately no i haven’t