The DT file SONG OF THE SEALS doesn't credit the writers, so is another candidate for an update. An earlier thread on the subject did include the credits, however: Tune Req: Jean Redpath's Song of the Seals.

Stewie quoted the relevant bit of Jean Redpath's sleevenotes, too:

"This rather arty song (poem by Harold Boulton; music Granville Bantock) has a chorus which touches something so close to the heart that it has been 'recognised' by those born as far from the Hebrides as the Calabrian Hills of Italy. I learned it from the singing of Father (now Canon) Sidney McEwan."

That comment suggests strongly that the chorus isn't traditional at all, though many people may fondly imagine it to be. Bantock certainly used Hebridean idioms in some of his compositions, but there seems to be no evidence that the melody here was not his own.

Copyright in Britain is, I think, "life plus 70 years", but I can't promise I'm right about that.