It would seem logical that the same sculptor made the Airfix WWI Germans, British Infantry, U.S. Cavalry, Arabs, WWII Japanese, Sheriff of Nottingham and probably some others.
The WWI Germans, British, and U.S. Cavalry sitting posese have the unusual left leg out. The Arabs and WWI Japanese have the same pose running with hand up and rifle up. Cavalry, Arabs and Sheriff of N. have the same horses. I supposes he used basic masters and shared with each job.
I don't have the book. I decided not to buy it because I thought it would just be a big catalogue, not history. But the Swoppets history book (now 2 editions) mentions a shared sculptor between both companies, but he was the guy who did the last generation 54mm such as the nice U.S. Cavalary with foot poses.
Our first grenade thrower has probably since long passed on. I would have loved to go to his house as a kid and see his shop ... !