A quick look at BJP Almanacspst WWII shows they were introduces just after WWII in 1945, the last reference is in 1955.
Immediately after WWII there are quite a number of new British enlargers, Gnome the most popular. Some must. have been making equipment for the Government/Military during the war. Gnome, Technaphot, WWiliamson. Then new enlargers from Blumfield, Envo ,Johnsons, KLB, MPP<Omega (British), Peckomat, Photax, P.P.l., Reid, that's by 1948 and followed by De Vere.
Many of the companies were short lived. We had severe import restrictions until the early 1950s.
Ian