Personally, I would say continue your a levels at another college or if not maybe redo the year. For the most competitive jobs, its best to do a levels, and you will end up getting a better degree and have the experience of going to university. If you feel a levels aren't for you, then try the open uni as they don't actually have any entry requirements, so that might suit you. It is possible to study a levels at might, but i honestly think a school environment is better, you might get distracted at home, and its good for your motivation to be surrounded by people who are also doing a levels.