Hi, thanks for the reply.
I haven't contacted VMCC directly, just looked in their library. They have records of frame numbers for a number of British makes, but not Excelsior.
The frame I have is superficially similar to the C2 in the pictures you've posted (telescopic rather than girder forks, plunger rear suspension) but specifics of the forks, triple clamps and frame are different. Part of the difficulty is that there were so many Excelsior models with the same basic layout at that time; Roadmaster, Consort, Universal, Courier, Talisman and so on. It's only when you look at the specifics that you start to notice the differences. Hence the plea for anyone who has a bike withe C1 prefix in the frame number.
Still searching...
Cheers