Hi ashlee
As far as I know they use the PILAPT aptitude tests, although Im not 100% sure. Unfortunately, theres not much you can do to practice for these. Apart from maybe trying to read the orientation of a figure holding a shape in each hand when it is upside down, back to front etc, and deciding what shape is in what hand. I doubt this would even help that much though!
Apart from that the tests are to do with coordination using a joystick, multi tasking and concentration. Personally, I found the concentration ones the easiest and the multitasking harder. But I wouldn't worry anyway, the best thing is to relax and imagine you're at home on your PC playing a game, and also Oxford aint gonna say bye to your cash unless you're pretty badly uncoordinated and very slow.
Good luck
Divet II