That on publishing from a man who just published: "I'm a trained musician and I have a pretty good ear, but I wasn't even able to determing what key it was in." (Don Firth, above)...and, voice aside, Don, the top-line notes played on recorder and keyboard are DEFINITELY as on the score; so, if you do have a trained ear, you should be able to tell the key from the instrumentation on The Water is Wide, and When I Survey the Wonderous Cross, at least.
As for Young Emma, the notation doesn't seem to be on the web, yet, but it is in The Penguin Book of English Folk Songs, which I don't have...?