Have been in touch with Stephen Foote of the Guernsey Society. We are going to link swap for the anthology site. Really usefully, Stephen sent me a link to D. H. Lawrence’s “The Man Who Loved Islands“. This story is new to me, and I have just read the introduction by Chris Jennings, who says that Lawrence:
“…was a friend of Compton Mackenzie who had met on the isle of Capri in 1925. Mackenzie objected that he had been used as a model for the character in Lawrence’s short story. There are, indeed some similarities.
Compton Mackenzie lived on Capri from 1913 to 1920. He then bought the island of Herm and Jethou in the Channel Islands. After financial difficulties, he sold Herm and moved to the smaller island of Jethou in 1923. In 1925 he bought the uninhabited Shiat Isles near to Harrris in the Outer Hebrides, Scotland. He never lived there but did live on the nearby island of Barra, where he built a house. When Sir Compton Mackenzie died in 1972 he was buried on the island of Barra.”
According to Wikipedia “Mackenzie at first asked Secker, who published both authors, not to print the story and it was left out of one collection”.
When I was last at the Prilaux Library in St. Peter Port, I saw there was a good deal of Mackenzie material there, and I knew he had a connection with the island. But this is a great lead to follow up on both writers.