to the guy above, my A levels were dire and i got through. It's pretty much entirely your work experience and your essay questions.
As for myself, I screwed up on the maths test (I didn't even finish it in time, and pretty sure a good proportion of my answers were wrong) and thus didn't get put through to stage 3
extremely annoying to discover from a few posts above, that examples of the exact questions they use are flooded around the internet. If only I'd done a bit more research