A couple of observations.
The 1970s experiment in the Eng and Supply branches did not delay promotions for others by too much. Instant sqn ldrs or Greenshield stamp sqn ldrs generally had suitable experience outside, some were ex-service anyway and many were able to rely on their natural charm and ability to help integrate.
As to the police. The met police college stands on a part of RAF Hendon given to them in 1930 something when Trenchard was called in to sort out the Met. Furthermore, there were a number of senior police officers who were military but of course very many in that era had fought in the war.
Old Duffer