ORIGINAL: Cohen_slith
I see a Strategical Unit here as four engine bombers - which I do not believe UK had in adequate numbers in '39.
Not true, look at bomber 3, they had quite a few Wellingtons in Sep 39. Probably enough to justify 2 units in game.
http://www.niehorster.org/017_britain/39_raf/_raf.html
I count 19 squadrons in bomber 3 of Wellingtons. That's 6-18 planes per squadron and production would be adding more all the time as it was a modern new aircraft currently in the production cycle.
Edit: Oops, one of the squadrons was in New Zealand, so only 18 not 19 were in England sorry. That's still quite a powerful force of 4 engine planes at the very start of war.
Jim