Hi Flo324,
Good luck with your assessment after Christmas, it isn't as stressful as some make out. I actually enjoyed my day at OAA and I'm sure you will too!
I'm flying for my PPL (under 10 hours only so far) but I really would not worry about having any experience as the FPP is designed for those with little or no flying experience.
In terms of practice I would revise GCSE maths and physics as much as you can. Browse these and the OAA forums for information and advice of the rest of the COMPASS tests.
Good luck with your application.
FO_DJ