Basically looking for something that would grant a better understanding of British folk music going from it's early origins in (probably?) the middle ages or earlier through the centuries. I say English language because I want to include places formerly under British colonial rule as well if possible.
There's a (quite large) 2017 book on my bookshelf called Folk Song In England by Steve Roud, which I'd recommend as being a mixture of readable and scholarly, and which does well in soberly stripping away some of the mythmaking that went on in the 20th century about folk song and its origins.