Here is a wonderful songbook by Paul Hardy of well-known Christmas Carols released under Creative Commons “Attribution Non-Commercial Share Alike” licence (c) 2012https://alive-drumming.org/wp-content/uploads/2018/12/pgh_xmas_tunebook-2018-12.pdf
What we like so much is that the format is minimal and straightforward, with a simply-written melody, chord symbols and a single verse of lyrics. Great for busking or developing one’s arrangement. Moreover, they print beautifully as they are not scans but typeset documents.
Thanks go to Paul Hardy for developing them. Check out his page for more details and to make contributions –
Available at Paul’s website – http://www.pghardy.net/concertina/tunebooks/index.html