A couple of websites say that "I don't know who you are, sir, but you've done me such a power of good" – or some variant – was a catch phrase popularized by comedian Spike Milligan on the Goon Show, c1959. Specifically, it was a line spoken by the character Major Bloodnok (or Bloodknock). This page contains a transcription of one episode, titled "The Call of the West" which contains the line "Ohh, that's done me a power of good, folks!"

Being an American, I don't know much about the Goon Show. Can anyone confirm this? So which came first, the catch phrase or the song?