Well, that is the first thing you need to figure out, no point doing anything else till you know what you want to do. If worst comes to worst you can always fail out of yr 12 then go to a different sixth form and repeat A-Levels. Which is what I did after getting 3D's and a U. I then moved to a different school and got AABB in year 12. I'm now studying for an Msci in Biochemistry wondering whether or not to do a PhD or a GEM.
Point is, there is still time to decide, even if this year doesn't turn out as expected. So don't worry, but do decide what sort of career path you would like to do. If you don't know then figure out what things you find interesting.