Bonjour Doc Rock.

Nice to find someone interrested in French Folksongs.

For songs from Center France :
Try www.CMTRA.ORG and look for Millien's "Chansons populaires du Nivernais et du Morvan" (7 books, the first 4 are worth the money to me) and Barbillat-Tourraine's "Chansons populaires du Bas-Berry". Some of Malicorne's song come from this book. All these books contain lyric and scores.
This site sells true French Folk music CDs.

For sea shanties and sea songs : Le chasse-maree

Hope this helps

Laurent