Sycamore
To the best of my recollection it was Mr Murchie (the Lighthouse Keeper) who telephoned the Emergency number to report the crash. It is possible that others on the Mull also called 999 on mobile phones; however they were hefty pieces of kit to lug around - being the size and weight of a standard house brick in those days.
Certainly the timing of the crash was logged by the Lighthouse keeper as a matter of routine. I was informed by HQSTC of the crash just after my arrival home that evening.
The SuperTANS recorded an initial power-down time of 16:59:36Z so I would suspect that the initial 999 call would have been made at approx 1700Z.
If you are desperate to find out definitively who dialled 999 from the Lighthouse then I suggest you contact Trinity House.