Don (and Steve as well),
The 8-track quarter-inch format may
have been more common here than America, as part of the "home music
recording" industry. Because this serves people composing music in their
bedrooms (on an overcrowded island!), customers either bought an 8-track
quarter-inch machine or a 4-track audiocassette machine, the latter often with a
built-in mixer to save even more space. I picked up my 8-track for only 250
British pounds. I saw no need to get another, because even if a track fails, you
can still fudge things so that four remain working.
The 8 track Quad player I own plays 4 tracks one way,
4 tracks the other way = 8 tracks. I don't believe I've ever read about a
8 discrete track 1/4 inch tape head.