Helliar Holm Lighthouse was built in 1893 and vacated, when it became automatic, in 1967. It is technically on a tidal island off Shapinsay, but it has to be a really low tide before it can be accessed on foot. The Northern Lighthouses Board has recently passed the lease, and responsibilities, to the Orkney Islands Council for reasons outlined in this item from The Orcadian.
There is unlikely to be a new lease of life for the accommodation linked to what is now a navigation light. The account of the recent history of the house, to be found in the Orkney Image Library, is worth reading. It conveys - especially in the Comments section - how the decline in a way of life and the decay of buildings can happen so quickly.
Scottish Islands Explorer - tries to combat decline and decay