Much better news -
After a battle with the local DVLA office manager on the phone this morning, I persuaded her to ask Swansea. She spoke to Head of Policy, who told her that my SVA was acceptable - I now have a registered car, on an age related plate.
Caterham, both midlands and south, were very helpful when I contacted them regarding the IVA and registration, and took the view that it would be highly impractical to try to get my car through the inspection. Among other components, even the shock absorbers would have to be changed (edges of spring pans too sharp).
Paul