Thanks for the positive comments folks. I was mistaken in assuming that the Somerset tunes derive from 'Rushes'. Mr Barrett's tune (the one collected by Hammond and published in Marrowbones) is not in fact similar. What it does resemble is a tune given to the Scottish collector William Christie from an Aberdeen singer, which can be found in Vol. 2 of his 'Traditional Ballad Airs' (1881). (I once downloaded Christie's complete collection but have since lost it and the URL because of a disc failure; however it must still be out there somewhere).

Of the three Somerset tunes, I don't now think that Tom Spracklan's was related to the others. However, that should be judged by someone better qualified than me. What all three do have in common though is that they do not have a B part; i.e. they are eight bars repeated. Fine tunes nevertheless.