18 months is a realistic timescale for guys who've completed the licence modules prior to leaving the RAF. Walk away with nothing and it could take you 3-5 years to pass all the exams and acquire the necessary civil aircraft experience before licence issue and certifying positions become reality.
Dodger,
Whilst I appreciate studying for a licence in an operational environment is basically a non-starter, you must make time to study back at your main base. Time served, rank and status held is irrelevant on leaving the forces and you will work as a mechanic until you've got a licence. Make it your primary goal to get as many modules under your belt before jumping ship otherwise it could be a number of years before you get back to a level of responsibility and authority that is similar to what you may have been used to in the mob.
Plenty of us have successfully made the transition to civil aviation. The opportunities and rewards are out here but nothing comes free, you will have to work for them just like everybody else.