OK, thanks.
Actually believe it was called the Cygnet (a baby swan of course), although that may have been spelt Signet (as in ring!)
As already established it was built in 1955 by William Johnstone (known locally as 'Blocky Bill') of Quadrant, Kirkwall utilizing a Douglas motorcycle engine. Unfortunately I can't say what that was replaced with, but I'm working on it! William Johnstone had founded Hatston Concrete in Hatston and made his fortune.
The bodywork was, I believe, built with the help of Herbert Rendall, a local plumber and tin-smith in Kirkwall.
The car was originally registered BS 1111 (originally allocated in the 1920s to a Rover and which was later transferred on to Bill's Rolls-Royce) and has recently been restored. It is now red (as I see you said before..) and belongs to a Walter Scott; it's still in the Orkney Islands.
I'm still trying to find out the other info requested!