Top economics degrees in the UK pretty much all require A-Level Maths (often at A*/A grade) and the very best often ask for A-Level Further Maths (e.g. Cambridge, LSE, UCL, Warwick etc). My advice to anyone who wants to study economics at degree level would be to take Maths and Further Maths. Aside from those, any subjects will be fine to be honest. For example, economics degrees frequently require you to be adept at essay-writing and so subjects such as Economics, History, Politics, English Literature etc. will be fine. In addition, economics increasingly draws on areas of applied mathematics and subjects which use mathematics intensively; therefore, taking subjects such as Physics and Chemistry (and perhaps also Biology) will also be very helpful. Also, languages are equally good, and perhaps increasingly useful especially for the job market later in life. Basically, my advice would be that if you are set on studying economics at university, take Maths and Further Maths plus whatever combination of one or two more subjects that interest you. This does not have to be economics as all courses will assume no knowledge of economics; however, this may be helpful for giving you a head-start in some courses. However, it is worth noting that almost all top economics degrees will assume a fundamental knowledge of pure mathematics.