Very many thanks for your offer. After my first posting I’ve received a lot of information and learned a great deal about rear hubs of that period. Unfortunately the one thing that emerges is that the 1927 hub / brake assembly has little in common with the later device fitted to my machine which amongst other things incorporates a cush drive. In my ignorance I was hoping to perhaps acquire a hub / drum assembly and then use the remaining parts from my existing hub to make it complete. Unfortunately this has not proved to be feasible. I’ve therefore had to accept compromise and decide to go ahead and have my existing hub re-built into a 21″ rim, which is where I came in, not wanting to spend the money on the wheel rebuild with the wrong hub. Hope that all makes sense!
Many thanks again to the offer.