Only advice I can give you is what others have already said...learn the document you've been given back to front (you don't need all the info for stage 1 however, you will need it for stage 2 or at some point later on so you may aswell learn it now). Brush up on distance, speed and time mathematics questions.
Most importantly, don't get too nervous. There is no formal interview, and yes there are tests but nothing you wouldn't have expected as you're given examples to practise.
Be aware of making silly mistakes in the tests...i.e. they are multiple choice. One of my colleagues who is now training to be paramedic used to be an assistant ATCO in the forces. My colleague tried 3 times for NATS and was unsuccessful each time and they believe that one of those times was down to marking one question on the multiple choice paper against the incorrect question number. A small mistake which cost him dearly because all subsequent questions were then totally wrong. (I don't know why they didn't pass 2nd or 3rd time round...).
Good luck! You've got a few months ahead of you where you'll be waiting for results on different parts of the application process and personally, I find that the worst bit!