I found an unverified reference to the 1st Guards Brigade receiving a few Thompson SMGs in France in Feb 1940 and wider distribution by June 1940
Here’s a British Thompson Training pamphlet from 3rd July 1940, which was distributed to Guards Battalions, et al, as you can see below:
The British OOB only has two HQ units:
1930 – Dec 1942
Jan 1943 – 1946
It doesn’t make sense for the HQ unit primary weapon to be a pistol all the way until 1943.
A third HQ unit could be made from 1930 – Jun 1940, but the war doesn’t really start for the British Army until May 1940.
This game already takes many OOB liberties in the 1930s with vehicles and weapons, and I’m fine with that, it’s primarily a WWII game. 1930s scenarios can model units and weapons according the precise date if they want.
As far as WWII is concerned, to give the early HQ a Thompson rather than a Carbine solves the discrepancy for most of the war, and is easy to change.
cheers,
Cross