What a fascinating thread.
While you guys are sorting the id out, ( I do not have any expertise in this species, having only seen one twice ) I thought I would add some definitions to this listing business. But first, I assume that all concerned know of a discussion on this sub species, in British Birds 50: 246- 249 and British Birds 66 401 - 402. Apologises if you have already seen these references.
OK, some definitions
Great Britain - Great Britain is the largest island in Europe. "Great Britain" is the collective name for the three countries of England, Scotland and Wales. It also includes the small adjacent islands but it does not include the Channel Islands and the Isle of Man.
United Kingdom - The United Kingdom is made up of Great Britain and Northern Ireland. The official name "United Kingdom of Great Britain and Northern Ireland" came into use in 1922 after the constitution of the Irish Free State (1922-1937), the former name of the Republic of Ireland
British Isles - The expression "British Isles" is geographical and not political. They are a group of islands off the northwest coast of Europe consisting of Great Britain, the whole of Ireland, the Orkney and Shetland Islands, the Isle of Man, the Inner and Outer Hebrides, the Isle of Wight, the Scilly Islands, Lundy Island, the Channel Islands and many other smaller islands.
So, if you have a 'British' list which is using the adjective to refer to the term Great Britain, or if you have a UK list then you cannot tick this bird because the Isle of Man is not included in Great Britain or the United Kingdom. However, if your list is a British Isles list, then you can and also any bird anywhere in the whole of Ireland.
Colin