You never told me you were related to Phil Tanner.
I have a CD of him singing, where the sleeve notes say:
All the rights of the Phil Tanner songs, speech and mouth music were assigned to FOLKTRAX for registration and protection by his nephew, John Tanner, 25/1/67, and registered with the Performing Right Society and the Mechanical Copyright Protection Society the same year.
I guess this means they own the copyright of the recordings, but most of the songs he sang are very old and would be out of copyright.