I would recommend, Boslandew, that you read the conclusion of the House of Lords report, especially, though not exclusively, from paragraph 135 onwards, in which the committee studies the various hypotheses. It is a useful synopsis. The Lords study the WP change, VFR/IMC, the Boeing simulation, the MoD's incorrect use of TANS for historical purposes.
Their sign off paragraph states:
How could it be that a very experienced crew, having planned to fly VFR, having taken when probably visual with the Mull the appropriate steps to alter course, when there was nothing to prevent them flying northwards within sight of the coast, flew into the Mull? It is as Sir John and Sir William speculatively described "incomprehensible" (Q 342) and "astonishing" (Q 377). We shall never know.
To the point.
Hell, on top of the potential tie-bolt problem I referenced some days ago, they even point to the contamination of hydraulics on ZD576, which the AAIB specifically did not rule out as a(nother) possible cause.