Hi Malcom
I just now listened to Martin Carthy's version & it's not the same tune, I also gave a listen to the midi's & they're closer to what Carthy does. The above link to Australia - real audio- is no longer available so I can't check that.
I've never heard the tune used to another song so I can't give any direction there either.
If anyone can take what I could sing into a phone & make something out of that I'd be happy to make the call if they'd just PM me their #.

Barry