Having passed the selection day back in December, I can tell you that the pages of information on here should give you enough preperation for the day. The PILAPT tests are designed to test your natural ability, and even though you can technically practise for them using some software of the net, it may not improve your skills for the big test on the day. I did not practise for them, but I have been flying Microsoft Flight Simulator for well over 10 years on my PC.
Good Luck with the selection day!