The GS750 meets the age requirement and seems to be available in a non-chopped/cafe-racer/stuffed up condition.

Has a lot of carbs though, I detest the things. Maybe a single car carb conversion

or maybe I just learn to live with them?
The CX has frame issues from a sidecar point of view, but still a possible. The subframe looks like something that could be done with flat bar and bolted through tube.
There also seems to be the illegal/triggers broom approach with Enfields. If you follow the Indian stamping system for frames and engines it seems they made about a million bikes in 1967 and sold the last one in 1993

I guess once you have the historical plate no one will care until you crash it.
Prices may seem high if you are used to what they were a few years ago, but don't hugely worry me. I'm happy with the going rate on standard, maintained bikes. The mucked about ones I will avoid. The owners may think their artistic tendencies add value, but to me they need restoring.
Too much choice! Thanks for your help and suggestions.
Andy