Come on guys, if you need to revise long division and multiplication then google long division and long multiplication and you will find a plethora of useful pages devised for pre GCSE level that helped me to revise it. I have been to uni (not needed long division), i have worked at high level in engineering (not needed long division), so i needed to revise. The sites i found will have you dividing 3 digit numbers into 4 digit numbers in 20 mins guaranteed. It's not rocket science, just a simple process to follow.
And yes, you do need the ability to think with numbers when flying. Give yourselves the best shot guys, but don't worry too much about the maths paper.. the PILAPT, now thats another matter!
There will be some good people at these selection centres, give yoursleves the best chance by being as prepared as you can for every stage. When you get to stage 3, do more research than the next guy, work out your answers to the obvious questions, practice delivering them, but don't learn them. Work out where you can shine above the others and go and do well.
high-flyer