Many thanks BDA, MRN, JB Collier & SENC for all of your valuable comments. I will post on the same subject when I have concluded this to let you all know what I did.
OK - I guess the pictures explain the story of what happened to the damaged 23D4; for the record, although not apparent from the photo's posted, the damage to the collar was in excess of 50% of its circumference, leaving not much for the base clamp to hold onto.
I looked closely at the challenges I would face using the 45D with the screwed cover and decided this was going to be a headache, (I wanted to have the distributor body so orientated that the HT leads would have a tidy route to pass through no's 2 and 3 inlet tracts on the manifold.)
So off I went looking for a replacement 23D4 body or having the 45D distributor changed to a clipped cover.
Ultimately, I ended up contacting Distributor Doctor (UK) who, (much to my surprise tbh) advised that they could repair the collar on the original unit.
The results are as you can see. I am not about to explain what they actually did, as the photo's are self evident and there are technically bright guys on this forum. Note however the brass dowel, (there are 2, orientated 180 degrees)
The service was brilliant, I posted on a Friday and the unit was back the following Sat; upon receipt at Distributor Doctor they sent me a detailed quotation for me to approve before they commenced work. (I wish machinists who did the work on my block and head did this....the number of times I've lived through the "how much?
"
)
All in all, I was very impressed and I honestly cannot recommend them enough.
Thread closed I guess.