Booke23 makes a critical point, to enter NATS above the exisitng age threshold you have to have had experience as either an ATCO or an AATC (or whatever they are in Trade Group 9 this week
)
As someone who came in after 15 years in the Mil, I'd reccommend just joining NATS straight away for several reasons. Why anyone would want to join the RAF nowadays is beyond me
However, if you do go the RAF and then into NATS route, as others have said above - I'm afraid it is right back to the beginning. After 15 years in Mil ATC I was only exempt from 1 Nav exam at the college. This must be a roaring success of the MOD in preparing its serviceman for civilian life....
Am I glad I left......too
right. I work a fraction of the hours and get paid twice as much .......
Choose wisely .....