To answer my own query, when I took the release bearing into the factor they came back in 30 seconds with the correct one, either as a graphite or roller bearing alternative!
The irony is that it is the one that fits the more powerful Hunter/Sceptre range, and I have now, 35 years after deciding that the Ace was not a practical everyday car and buying a Ginetta G21 with the Sceptre engine, found the first part other than the headlights which is common to them both.
Some years ago there was mention of creating a parts list, did anything come of it?