I do detect a difference when I listen to your WISTWC. The rest of the songs are sung out of pitch, off key and in a ridiculos accent, but WISTWC adds a touch of twee to the mix. As Don said, try to sing honestly.
Doesn't have to be perfect (or Sunday best), in fact that renders it bland. When you sing WISTWC, you need to be living out the words. That would call for emphasising certain words, for putting feeling into it. If you weren't so closed-minded about 'Your Own Good Culture', you could pick up a lesson or two from Jewish paraliturgical music (piyutim).   

Stu - I keep playing a line, singing a line, playing a line...and listening to others too, of course, etc. And that's one thing I am very sure of - working on the TUNES is a good thing for an English folkie to do.

The tune is far from the most important part of a folksong. The important part is getting the story across.