So, now the mast issues begin.
And... luckily for me, they are handled in different ways. Yee Haaa, just what I needed ... more mystery to unravel.
Anyway, following advice I had received, I managed to secure the loan of a copy of Masting and rigging the clipper ship & ocean carrier : with authentic plans, working drawings and details of the nineteenth and twentieth century sailing ship by Harold A. Underhill. from Internet Archive.
https://archive.org/
The attached images detail most of what I was looking for in relation to the iron mast sections, but now adds the very real possibility that a mixture of iron and wooden fixtures would have been utilised across the vessel.
So, here is the first instalment of fixtures and fittings for the iron part of the masts.
Updates to follow.