I never studied any "modern greats" courses at school but felt that the sciences seemed too restrictive with the Arts lying at the other end of the spectrum. Economics, as the queen of the social sciences, seemed like a good compromise - a subject where you don't get too many lectures per week, are allowed to go at your own speed, tackle things your own way to an extent, yet it's not a hippies' course (and hey you get a £50k/yr job at Goldman Sachs at the end of it all).
Edinburgh University's Economics department excels itself. Scotland's universities prefer breadth to depth, and so you can study Economics, English and Physics in your first year if you like (although the most popular combination is Economics, Business and Accounting). The first year of Economics is a gentle introduction, with no mathematics. However, you need to take accompanying intermediate courses in maths and statistics in first OR second year if you wish to study Economics at Honours level (ie years 3 and 4). In second year, the course becomes a bit harder and has some boring-but-not-too-bad algebra. As in first year, you have a certain number of subjects you need to take (I took Economic History and Politics) in second year. At honours, you pick from a very wide selection of honours courses, from the history of economic philosophy through international development to econometrics. Edinburgh may start taking your background in to account when deciding whether to admit you, so the normal minimum grades of BBBBB at Higher and ABB at A-level may not apply to you if you're the first from your family to go to University or come from, say, a state school in a deprived area. Edinburgh may have a reputation for being "English and posh", but there are only around 35% English (compared with 50% Scotch) and the number of privately-educated people at Edinburgh is no worse than York/Warwick/Cambridge etc. Hell, 99% of people here will be nice to you, so why care about their backgrounds? Apply!