The "Folk Alphabet" was written and performed by Fred Wedlock, a British folk comedian who also had a hit with the "Oldest Swinger in Town". It's on an album called: LIVE(With Chris Newman). I've just tracked it down myself after years of searching - all I knew was the line "A is for as I walked out as all good songs begin ...".

He's just set up a website at http://www.fredwedlock.net/ and I believe that he's re-releasing the albums on CD within the next few weeks.