Many thanks to you all for your time, information and patience with a newbie. It looks like I'll have to learn the Navvies version for a change! The original has been a favourite song of mine for a long time. Special thanks to Joe Offer for his detailed posting, and to Jim Carroll for Ganger McGlynn. I've tried to post a reply earlier, but had no joy so far, so hope this works.
Best from eldergirl.