Special VFR is only relevant to aircraft in Class A, D or E airspace which are either unable to comply with IFR or do not wish to. An example would be transit of the London TMA (permanently IFR) in 'visual' condtions by an a/c of less than 5700 kg. Or flight at night in Class D airspace (all night flight in the UK is under IFR even in VMC) by a pilot whose licence privileges do not include flight in circumstances where flight under IFR in Regulated Airspace is mandatory.
Under no stretch of the imagination is SVFR flight applicable to the flight of this Chinook near the Mull, even Machrihanish MATZ and ATZ are only Class G airspace and clearance to transit such airspace requires compliance only with the normal VFR/IFR weather limitations for Class G airsapce.
Walter, this is another red herring, as is the idea of little green men planting spoof beacons around the Mull....
The basic point is that there is no clear and obvious proof of what happened which is beyond any reasonable doubt whatever. For that basic reason, Wratten and Day's verdict is fundamentally flawed.
My own opinion is that, had the pair of them reached any other verdict, MoD would have been involved in several very expensive compensation claims running to several millions - hence they blamed the pilots.