FJTP, quite right but wrong date. Glasgow Bombplot had closed before the end of the '60s. It may have been the one that moved to Gernish in the Outer Herbrides.
The other high level bombplots at Ouston, Haydock and Kenley all closed and moved to Tumby near Coningsby, Lindholme and Dunkeswell.
Ouston had been able to score popup attacks on Newcastle but the presence of the increasingly busy airport and the undulating terrain made it unsuitable as a low level plot.
From time to time one of the plots relocated to Sleep, usuallu for competitions.
So, to answer the question, the bomber stream was probably flying up to the north east of Stornoway before running south with all their ECM on to be monitored by 112 SU at Stornoway.
OTOH it may have been no more than chance as they were on a common long range navigation exercise as part of a Group exercise.