What gilf says is certainly one way of looking at it. You do need to look at what interests you. Also what you're good at at school. However, the better qualifications you have, the better the chance you have of getting where you want to go, quicker. Future employers will be more willing to take on someone with better qualifications and has shown they are willing to work hard. Also those who have taken some kind of initiative in their own future. You should have a look at UCAS's own site.
http://www.ucas.ac.uk/
There is a lot to see here but if you look at "Courses", most paticular ones will give you a profile on why it would be suitable for you, and what qualifications you would need. Best of luck.