Let us go back to basics for a moment.
Has anyone ever asked the RN Officer who planned the sortie what the intended turning point was on the Mull?
Everybody seems to assume that it was the Lighthouse and that a misplotted map reference was inserted into the SuperTans - but a Naval helicopter Pilot would be acutely aware of the potential perils when coasting in on a strange shoreline; particularly so given the topography of the Mull. Moreover, the other Flight Deck member of his crew was a Navigator who would doubtless check the planned route.
It seems to me that it is at least possible that the planned turning point was the Helicopter Landing Site so that Lt K could familiarise himself with the layout so that he would not be going in "cold" if tasked into that site.