Isn't there a passing minor 2nd, rather than a 7th, as in Calon Lan?
G - Am - D7, rather than G-A7-D7 in Life is Like?

There is a version of Miner's Life that Frank Hennessy played of this group ( http://www.musique-sauvage.org/trad_welsh.htm ) doing it, but it's not on their site.

Chris