As a NATS controller, you guys and girls need to be learning any info given to you as thoroughly as possible, this is the tip of the iceberg - our manual of air traffic is a monster with some sectors worse than others. Get on the internet, watch some videos, listen to some ATC tapes even if they are from the USA and at least learn your name phonetically.
We are not out to get you at the interview but at stage 3 you need to have MULTIPLE real world examples of problem solving, how you've coped with high workload etc. Think Uni, jobs, exams, driving tests etc.
From my memory of aptitude test, they are looking for accuracy - the speed we can work on later. Make the planes miss, worry about the rest later, but concentrate on consistency not speed. They are designed to beat you but don't give up. In ATC you can never give up, it just isn't an option!!
Good Luck, you'll need a bit!!