Danny42c 2398
You are right. Most AFUs were based on SFTS schools.
I don't think the early bomb-aimers were "bribed" with commissions, - the Bomb Aimer I mentioned was 33, wealthy, and had spent two years as an A/c2 Balloon Operator. His Balloon Site was quite close to a pub, so he spent more nights sleeping in the pub, and dining there, than under canvas. I don't know how he managed to get on a Pilot's course.
The Wireless/Operators ordered to re-muster to Bomb Aimer were all Sergeants.
Until the beginning of 1942 the Whitley and the Wellington had two pilots, a navigator, two wireless operators and a rear gunner.
(A second pilot could get in ten trips before promotion to Captain. Later you were lucky to get one trip.)
One W/Op manned the front turret, the second pilot acted as the bomb aimer and spent the rest of the time attempting to map read, - looking for the coast, rivers and lakes.
In March 1943 Bomber Command decided they could no longer lose two pilots from one plane, so the second pilot was taken off the crew list, and navigators dropped the bombs until the new B/As came into being.
The Bomb Aimer sat next to the pilot on take-off and landing, then went forward for his map reading duties. When Gee and other devices were introduced, the B/A was give a seat alongside the navigator and helped with these gadgets, so he could be quite busy. The Front gun (Vickers G.O.) in the Halifax was rarely used. Fredjhh