ex-mudmover
A question better asked of the MoD's leading expert on the navigational/positional aspects of the flight, ACM Sir Michael Graydon (CAS).
He is on record as stating in writing, to Marshal of the RAF Sir John Grandy, that the aircraft was off course
"BY SOME MILES".
Of course, that would make every other witness a liar. As he wrote this in 1997, that would include the Board of Inquiry members and both ROs. It would also mean he committed a serious offence when (mis)briefing Sir Malcolm Rifkind.
If Graydon is not a liar
that would mean the intended heading was either to the West, tracking (e.g.) the east coast of Isla and over/round the Paps of Jura, or to the East (e.g.) up Kilbrannan Sound.
Of course, like all those VSOs involved, Graydon has never been questioned about this lie or its purpose. One is tempted to opine the only reason was to cast aspersions on deceased pilots. A cowardly act.