Only 2 Indian types were used in England. 'The 1200 cc Chief model 340B and the poor performing 500cc 741B Both are vee twins, relatively heavy and have LEFT hand throttles and gearchange on the RHS and left side foot clutches.
The WLA Harleys were never officially on the UK register and the equivalent WLCs were used. Same is in Canada. The brits were going for lighter Bikes all the time and these US bikes were different and although comfortable and reliable, they were heavy and thirsty and mainly used for road work. Convoys messages etc. They were sold but I doubt they were scrap. The 741 was grossly underpowered. NO Harley had a left hand throttle. THAT was exclusively an INDIAN thing going way back.
These bikes now are worth about 34000 for the smaller ones and 50,000 for the U models 90,000 for the Knucks GOOD and original. Regarding the BSA you mention some of things like that were IMPRESSED but the M20 BSA was one of the most common military bike s around. Also one of the Most uninspiring in many ways. The sought after bikes after the war when muddy motorcross started to become popular were bikes like the ARIEL W/NG 350 OHV and the G3L Matchless with telescopic forks (copied from the BMW bikes of the late 30's.. Nortons 16H 600cc sidevalve was one of the BEST Brit bikes with a "DRIVEN" sidecar wheel combo. ALL bar the 2 big Harleys easily affordable. The Knuckle head might go sky high as they doat times. IF you want one all bar them are affordable. Nev