What uni course and career?

Maybe try looking at different types of career on https://www.prospects.ac.uk/ ?

If you want to work as a research scientist you'd (probably) need to do a PhD. Most academic undergrad degrees aren't going to set you up for one specific job (just as an example, a lot of physics grads go into finance) so really for long-term careers you've got all the time you need to think about it.

Thank you for the link, I will definitely check out different career choices.

From research on degrees, I’ve narrowed down to:
Biomedical science (potentially lead to medicine or apply for the NHS STP)
Earth science (quite versatile and can lead to out in the field research work)
Mathematics (as a last resort as not only do I really enjoy the subject but it’s also an extremely versatile degree)

I will however research a lot more into all these, thank you for your help.

For biomedical sciences it's really likely that chemistry A-level would be required and for maths at uni, further maths is usually put as a requirement (if your school doesn't offer it then fair enough, they'll still accept you in that specific case)
No prob

Any biology related degree could probably take you where you want to go so look into lots of different ones and see which you like the sound of best. Earth sciences sound like a better fit for your A level subjects than things like biomedical or neuroscience as you have geography, but you could probably do any of them!