Identifying old Coventry bicycle

[dnc1]

That chain case also seems to have a large, removable panel with two screws at the rear wheel end. No longitudinal seam either.

 

[dnc1]

I could forward the photo on to the V-CC for publication in the club magazine if you'd like. It would open it up to study by many people far more knowledgable than I, but the downside is the timescale for a reply, we're talking months as the club magazine is only published four times a year.
I'll also show it to members of the Oxford section on our next ride in May.
There are usually only about 15 of us though, so it would be a longshot, but you never know.