I've had a lovely time searching a local second hand book shop, and bought a great book about English history in song, but no luck with the wheat watching. However, try this address - the tune is the one I know, but the words are different. There are Welsh words, there, though.

http://www.acronet.net/~robokopp/welsh/misydd.htm

I don't know how to do the magic.....

Best wishes, Penny