Thanks again Masato. I just heard that on the radio (while I finish some last minute Santa stuff) and thought it sounded like "The Water is Wide." I'll investigate it more later. Also, I'm not familiar with John Rutter, but also just heard one of the Wassail songs (arranged?) by him.

The German tune you referred to above as another tune for Herrick's Carol in the Oxford Book of Carols is "The Echo Carol." (Als ich bei meinen Schafen wacht)