Give them a ring, see what they have to say, find out when you can re-apply, Then get preparing for the tests, (you know what they consist of, and they arn't likely to change in the near future).
A big help for me was getting my girlfriend to make up mock tests for me, then I would take them in the time limits you get on the day, keep going over this routine, and your sure to be a whiz at them by the time the real thing comes along.
Good luck with your future application.
p.s. All the information needed to be successful in a NATS application is right here on PPRuNe, couple this with a lot of motivation, and you will be fine.
Ian.