The big frame suppliers to the trade were as you said Holdsworths, Claud
Butler's, Ephgraves and Stoke Newington Engineering. The last was
formerly known as Metropolitan Machinists. These were working during
the period of 1945 to late 60's.
Les Ephgrave built for Rory O'Brien, George Brooks, Don Farrell, Algurn
and some Purves when he was to busy. He used these shops frame numbering
system.
You also had one man band lightweight shops that built frames for the
trade and the lone artisans working out of sheds, lock ups, garages and
tiny workshops etc. Jack Jones, Jimmy Long, Vic Lyons, Les Ephgrave,
Ted Woodhall and Stuart Purves are good examples. Some started small and
expanded like Les.
I attended a 40+ (More like 70+) reunion the other week and this subject
who built what for whom came up over a pint. It was said by more than a
few there that if the lightweight shop was an agent for a famous maker
it was a dead certainty that these were making the shop branded frames,
George Brooks first used Clauds and then Ephgraves.
Croeso Cymru Joe King Nr. Maenaddwyn Ynys Mon Wales