I was there yesterday, out of about 27 people who went in 17 were "invited to leave", I was one of the lucky 10
Just make sure you read that document they gave you and try your best on the computer tests, I don't think there's any way to prepare for them really.
The first test FEAST is basically just a long online aptitude test with an English language part, DART is where you're controlling planes on an ATC screen and it gets progressively harder, more planes to control, more waypoints to send them through, more background traffic to avoid, etc. The last part of that test is "interesting" to say the least. I won't spoil the surprise
