I wouldn't go for 'well-rounded'. I think a straight-up approach is the best.
Become the absolute best you can be at your area/field, nobody wants a 'jack of all trades, but a master of none'. In other words, pick subjects that relate. It'll make your two years at A-Level easier, and enhance your prospects after you finish.
But because you're unsure, the best A-Levels (employability wise) are; Further Maths, Maths, Physics, Chemistry and Biology. Yeah, the sciences.
(Original post by Tahooper)
Arts & Humanities:
2. English Literature
3. Philosophy & Ethics
maths and econ are sciences......
And OP, it depends what areas of work you want to go into, if it's finance, then maths and econ are where you want to aim, if it's dentistry, biology, chemistry and some other subjects, im sure you get my point