Check out the thread below for a couple of books which are handy for reading before the tests and interviews.
http://www.pprune.org/forums/showthr...threadid=72514
Also check out this website for good info on the test and interview days:-
http://myweb.tiscali.co.uk/radar2001...rces/ATCO1.htm
You could also use the search facility on pprune and search for 'NATS interview'. There's been loads of useful stuff written in the past...I should know, I used it and got through it all (cheers folks!!!)
Dunno about the age thing as to whether it'll be a problem or not, but judging on a few of the posts recently I get the impression they can't afford to be knocking people back if they're good enough
Good luck anyway.
FB