I've met a lot of people, mainly in the engineering industry who are very successful and didn't have an A Level to their name.
I know this guy, in his late 20s who really wanted to do an engineering degree. When he did his A Levels he didn't get the results required to progress to university and obtain an engineering degree. Exams and stuff aren't his strongest attribute. He knew this at the time. So instead of sitting around at a desk and revising again for resits he spent his time applying to apprenticeships to literally hundreds of companies.
He got a good response and offers from different companies. He chose to go with Rolls Royce and works in the Derby plant in manufacturing, and research & development.
Fast forward 10 years to now: he now project manages an engineering project relating to the Trent 900 engine and has a team of engineering graduates under his wing. He's on quite a handsome pay packet too conisdering his age. He always says one of his main gripes is graduates with all those qualifications fresh out of uni can't do the simplist of things - basic fundamental engineering stuff. To him, having a grade next to someone's name is a bit crap.
The point is, A Level exams aren't the end of the world.