War Duties Police Observers
Further to the statement that the military "didn't train them for Police Air Ops units per se."
Correct. The War Duties Police Observers were a Cold War project. Both the army and the RAF were involved and although there was a degree of crossover this was a military project with nothing much to do with police observer training. Training was mostly in Chipmunks and Bulldogs (RAF) and Austers, Beavers Alouette II Scout and Skeeters (Army)
The War Duties flying survived into the early 1990s and and the crossover meant that many early police observers effectively served on both. There were numerous police trials from the 1960s and they utilized the War Duties Observers as pre-trained personnel (for obvious reasons) and it was some amongst them that went on to create what became police ASUs from 1980 (The Met).