Having spent several years researching the songs collected by the Rev Sabine Baring-Gould, I have followed a Cornish thread that has led me to songs that as far as I know are not shall we say in common usage at present. These are being added to a growing pile that I am convinced are unique to Cornwall.
The folk site www.wovenwheatwhispers.co.uk published an article I wrote titled 'Songs Unique to Cornwall'. Since writing the aricle which was based around the songs from my CD 'By Chance it Was', I am this year starting to perform the newly found songs here in Cornwall.

I am convinced there must be other sources, as Phil Beer says check out the book shops somewhere there must be some unsung gems waiting for an airing