Joe,
I'm not coming down on any side. I just transcribed what I heard from the original recording. I'd be happier singing 'They long did'... 'and battled'. The chorus wasn't in the original so we can only wait to see what Ruairidh and Brian can come up with when they get together. If we can identify the writer of the later version we may get somewhere. Currently we are looking at the Norfolk coastal towns.

My own guess is that Brian was right about relatives (as opposed to descendants) of Delf moving down to Norfolk during WWI to avoid the persecution of people with Dutch/German sounding names. If a relative did rewrite it as part of one of the Norfolk fishermen's choirs then it would be a small step back up the coast to Filey to being sung by the fishermen's choir there, Filey lying just to the south of Scarborough.