Are you specifically looking to gain a qualification in Economics, or are you content with just self-studying it? Khan Academy is extremely informative on Finance/Economics, so if you're just looking to increase your awareness of such matters then I'd definitely check it out - especially as it means you can study it in your own time, whenever you're free, without any commitment.
However, if you're intent on gaining an A-level in the subject, I'd definitely check out some past papers and Specs, as some of the exam boards offer different branches of Economics and test you in different ways (e.g. AQA, I believe, have multiple-choice questions whereas some of the other exam boards do not).