The wise thing to do would be to have 2 to 5 other career options - or jobs - in mind. Eggs in one basket and all that.
With regards to the UK Forces - some tough cutbacks are on the way including mooted "redundancies" - probably through recruitment freeze, natural wastage along with, in the RAF's case losing one or more airbases and aircraft types. And the Navy's carriers are still not commissioned yet!
The Army are recruiting strongly however - I do not know how close they are to reaching maximum this FY.
Good luck!