Abz217. You can find all the offical hints & tips on the NATS site:
http://atcocareers.co.uk/pdf/Hints-a...Three-Days.pdf
There is now an official mention of the numerical paper.
On my test there were two aircraft specification questions.
The dress code for the event is smart/casual. I think the idea is so that you blend in with the company dress code policy.
No calculators are allowed. You have to do all the number crunching in your head or on scrap paper.
Good luck.