I'm a mature student, well into adulthood. Depending on what you want to do, the two MUST grades are AT LEAST a C in both Maths and English language (sorry literature wont count). That is it. Most employees expect those two as a given.
Now if you are heading into a specific career then maybe a science or the like would be added. This of course doesn't cover college/university entry and you would need to check the specific course and place.
For a £60K job you would probably need a Honnors Degree, with years of experience to back it up, it definitely isn't a starting wage -the average working amount is £24K. Nor is it a wage you would attain in your early career, but something on average you would get in your 50s etc., and only when you were at the top of your chosen career, a bit like Olympian. £60K is pretty unreachable for most, where as something like £35k would be realistic for a life career. It entirely depends on the degrees you have and job experience as well as the career you choose.
I would recommend getting the highest feasible grade you can in each of priority career driven subjects, don't worry to much about the others EXCEPT English Language and Maths.
We have roughly 13 weeks to go to the exams, so plenty time of time to get head down, start revising now, do extreme prep and you've got better chances of getting the grades you want
PS one thing that will make a difference is the University you go to - so if you get a chance to go to Oxford/Harvard or in the top 5 then go there.