TheAerosCo
Certainly some of your questions have been answered, however here goes:
I was an ATCO at the Scottish ATCC at that time and I personally videotaped the radar recording.
A friend (and next door neighbour) was the ATCO on duty at the time. He never heard any R/T call but from the tape transcript there was a single call, just the usual initial call as I understand it "Scottish - callsign".
There was nothing on radar, bear in mind that the 'nearest' radar was on the island of Tiree and the only other possible radar at Lowther Hill could not 'see' over all the bumps between it and Mull of Kintyre.
Machrihanish ATC was closed by then.