Sadly enough all those places are really too far away from me to visit in person.
I am on the other side of the Atlantic
But I think I get the overall idea...
What is interesting though is why is there so little material on the Mark IV out there? Given that it was logically considered an improvement over the old version and was installed on the new boats including those built some time after the war and also probably over time retrofitted to the older ones...
Should it not be more common today in both the surviving boats and the documents than the Mark III?
Anyway if there is any chance to get a scan or just the text or any digital version of the OP1442/1442A/1056A pamphlets... That would be absolutely amazing!