As a 'student', the following are non taxable:
- Student Loans
- Grants
- Contributions from your parents
- Scholarships
- Research Awards
- Housing Benefits
- Gifts and loans from relatives
- Income from ISAs
- Prizes won by students due to academic excellence
Anything else you earn from an employer even as a 'student' is taxable within the rules laid down by the Inland Revenue. Sorry !!
In the NATS case, you are not a 'student' in any case, i.e you are not following the Higher Education path. You are an employee who is being trained. You'll be taxed just like the thousands like me who have gone before you !! Remember though that it is a sliding scale. Nothing on the first £4745, 10% on the first £2K (approx) after that, 22% on the next £29K approx.
There are other rules for travel and related expenses. NATS have agreements on these with the Inland Revenue and you will be told what you can and can't claim (along with any limits) when you start your course.
Cheers