Some of the topics from RS come up in Philosophy, which is more commonly "accepted" as a preferred A-level from top tier universities, and approaches those topics from a more general perspective. There are also other topics in that as well, which you may find interesting.
But as previously stated, unless you're aiming at the few "elite" universities which tend to be slightly more preferential about A-level subjects, as they get so many applications from people with the necessary grades already they need a way to filter those a bit more, it won't make much of a difference. For most "arts" subjects (i.e. humanities and social sciences) they aren't too choosy about specific subjects taken provided you do well in the ones you do take.
It does depend somewhat on what you want to do at uni (if you want to go at all for that matter, as it's not actually a requirement by any means, despite being made out as much by much mainstream media - fortunately, unlike in the US, there are a lot of roles you can pursue without a degree, many of which lead to career level positions) however. If you want to do e.g. Economics then you'd probably want to take Maths to put forth the strongest application. For the sciences, you need to consider which science subjects are required for the degree you're interested in - usually the named science of that degree (e.g. biology for bioscience courses, chemistry for chemistry courses) and many have additional requirements of other subjects (e.g. maths as well for physics, chemistry is required for a number of biomolecular "themed" courses, e.g. genetics, biochemistry, biomedical sciences).