His flying may be credited towards a PPL only if conducted by a QFI. If it was conducted by some AEF pilot who was neither a current QFI on type nor the holder of a civil FI Rating, it is considered to by air experience passenger flying only and is not creditable.
If he has any gliding (or Vigilant motorglider) time, he can count 10% of any pilot-in-command time, up to a maximum of 10 hrs.
He is more likely to pick up bad habits from unqualified air experience pilots than he is from a civil FI!
Back in more enlightened times, hundreds of aspirant RAF pilots received 30 hours of PPL training at approved civil clubs under the Flying Scholarship scheme, then went on to join a University Air Squadron, receiving about 30 hours per annum with RAF QFIs.
But sadly, the beancounters have done away with Flying Scholarships and have reduced the UAS system to a shadow of its former self. Instead of arriving for formal RAF flying training with around 150 hours on SEP aeroplanes, the student of today will be lucky to have 30 - and no solo aeros, no solo off-aerodrome PFLs and not even solo glide circuits....
It's a ******g disgrace - like so much of the RAF of today, sadly.