This is a wonderfully amusing song which I very much enjoy singing. I first heard the text as a child in the early fifties as part of radio broadcast on the BBC. Gerard Hoffnung, if I recall correctly, related the story as part of an after-dinner speech at some banquet or other in London. I first heard it sung by one Noel Murphy on Wally Whyton's, "Folk-Music" on the British Forces Broadcasting Service (BFBS) round about 1982.
Imagine my surprise at seeing this song performed by "The Dubliners" at one of their concerts in Bremen in 1992. I'd been singing this song for yonks and somehow considered it as "my" song and not even folk-music. That's the Irish for you, any song an Irishman sings becomes an Irish song.
By the way, "The Dubliners" title for this song is "The Sick Note".