Not that I know anything, but I would say that folk music is still big in Wales, especially if we include bands who don't sing exclusively in the Welsh language. Obviously the Harp is the national instrument of Wales along with the Welsh Pipes. I admit that the pipes don't get the airing that they should.
Since listening to Radio Cymru, I've been surprised at how much folk music is played, particularly in the mornings. I can't really think of any other BBC radio station that is so awash with folk music outside of it's dedicated folk programmes.
Going back to names, a few more to add are Mary Hopkin and her daughter, Jessica Lee Morgan; The Moniars, Elin Flur, Georgia Ruth, the Henessys, etc etc. Can we include The Gentle Good, Joy Formidable etc? I'm going to be pushy and say that my friends: Barlow Cree deserve a mention, and finally for now - who doesn't love Max Boyce (now and again).
Sorry to but in again - I thought that Siaron had mentioned Meic Stevens, we cant miss him out