>>10949204I found a decent picture of the WW2 British Infantry set that showed the Thompson. You can see in the 8th Army pic you posted that the Thomspon there has a front grip and cooling fins for the barrels. This is the earlier M1928. But the British Infantry set has the later model M1A1 with no forward grip or cooling fins.
As an aside, it's pretty remarkable that Airfix went through the trouble of all these details even if their choice of SMG is a bit of an oddity.