I have bought this early WM20 a couple of days ago. It still has papers from Northern France from 1949. It is a very complete WM20. Fitted with early toolbox with lock, the original oil tell tale and a lot of correct early parts (f.e. bellmouth, oil lines, original BSA footrest rubbers, early domed glass CZ27, MT1130 etc.). It's now in the hands of a Dutch collector in the South of the Netherlands.
It will need new tires, wiring and a overhaul of the engine and gearbox.
Bob, almost certainly. The lack of later parts means it can't have stayed in service long. Almost certainly a BEF survivor that reappeared with a new identity after 1945. The populations of Northern France and Belgium have a thousand year history of hiding away anything left by passing armies !