There's not a lot of prep you can do before you go, just do your best on the day. Make sure you have a good night sleep before hand and eat breakfast in the morning - improves brain power.
If anything, brush up on your basic time, speed, distance calculations and get some questions ready for the ATCO's when you see them.
Review your application form and if you answered truthfully in the beginning, you shouldn't have any problems with being inconsistent between the form and your interview - they WILL pick up on it and ask more and more questions in that area until they are satisfied with your answers.
Good luck anyway!
HS
