Further to what Malcolm posted above about the tune Martin Carthy uses, some more information from a recent Guardian interview with Martin:

http://www.guardian.co.uk/music/2011/apr/17/martin-carthy-interview-ed-vulliamy

The mention of that song raises a question: who wrote that giddy tune to "Famous Flower of Serving Men" which also drives the far more famous instrumental at the end of Fairport Convention's "Matty Groves"? One does not need to know the song to savour the story:

"Well, it was 1966, Swarb and I were in Skopje, doing a festival to say thank you to countries which had supported Yugoslavia. And Hedy West, whom Bob Dylan cites among his influences, was there, messing around with the tune of a song called 'Kate and the Cowhide' from Utah, written in 3/4 time. She sang a version in 9/8, and Swarb and I were flabbergasted.

Well, I went on to use it in an arrangement of 'Famous Flowers' and Swarb joined Fairport and added it to 'Matty Groves'.

That's what folk music is: the intuitive nature of the whole thing among people who love messing about with stuff and coming up with something else to keep the continuity going; people who aren't intimidated by how venerable it is. A song cannot survive if it is not being played – it is either played or it perishes."