The version of the song that you have heard sung by the Wilsons was put together by Richard Grainger several years ago and is based on a traditional ballad, one version of which is given in Roy Palmer's "Boxing the Compass".
I don't have all the words, but if you're still stuck I could probably get them, in which case e-mail me at sdawes2262@aol.com.
But why not instead contact Richard directly? I'm sure he'll be happy to help. richard.grainger@onyxnet.co.uk should find him.