The aforementioned Cornish song book, although not really containing a vast amount of 'traditional' material is still a great place to go. I was born in Devon in 1953 but my mun is a Tonkin from Falmouth and we spent a large amount of our early years in Cornwall. My family are also Methodists and very musical and we actually did used to spend time around the piano as a family singing songs from the book. I recently was in Falmouth clearing out my aged Aunts house and found her copy which is in far better condition than mine. We also took charge of the fine old broadwood upright which now resides in my sisters house for another generation of of kids to learn music on. I've just been working with Exeter singer Dave Lowrey who aslo has a great affection for the book and has recorded 'The Cornish Smuggler' from it. In conversation with Cyril Tawney before he passed away, he also indicated a similar early exposure to music in precisely same way. There are plenty of copies still to be found if you search the old bookshops. Might base an album around it one day---