And with a Sea Level temperature of 9 Deg C, the crew would be working on a 'rule of thumb' freezing level of about 4500'
The pathetic so called icing clearance for the Mk2 was 4 Degrees, to be expected at 2500'.
IFR was not an option, and contrary to CAZ's assertion that Flight in accordance with IFR would be required in the vicinity of the Mull ( I know he is only quoting the BOI report), low level VFR along the coast was easily achievable.
Why no turn was made to follow that plan will never be known beyond any doubt whatsoever.