Ahh, a production run of 90 or less explains why our local Asda wasn't packed with them, doesn't it ?
By the mid 70s I'd got into cars and had a Marcos, which was very much the same sort of thing. I'm betting if you had the Piper in the 70s you would have been to the Marcos Owners Club weekends at Donnington in the Midlands ? Although it was billed as MOC day we used to get all sorts of sporty cars from the 60s turning up and I can remember being there one year with a line of Pipers parked up on the grass. The large rear screen always took my eye and I bet it must have got very hot in there at times.
Brian