Trainee Salary £10,678.
£60pw Accomodation.
These are 2009 rates published on NATS website. They have all the info you need.
Small salary, but if you compare that to being a mature student, i think you should be pleased. As for moving your wife and kids, i think you'd struggle, finances aside, its a demanding role where you can fail at any stage without the right dedication youd be uprooting them again in no time.
This site has all the info you need:
FAQs - Jobs and careers at NATS