Thanks for all you suggestions and assistance - I know of I Will Never Marry but much prefer these older words.
I do another similar song 'John Riley', popularized by Joan Baez, which is a similar sort of thing relating to a lost sailor (who returns in the end with a test of her fidelity) and there is a whole rake of these sort of songs out there - this version just appealled more to me lyrically.
I will certainly try the Roud number and root it out that way.
Failing all that I can't go far wrong with G, D and A!! :-)