It was not complacency W, but scared that they would be caught, the decisision making process was nothing to do with flying weather, instructers lack of training or any other smoke screen. This was about we better get home before we get caught by the husband and that is what is criminal about the events, even PPL's should be able demonstrate a level of professionalism towards safety even when the thing in there pants is taking over. The forecast for the complete weekend was, as I am sure you will agree extremly marginal and you have to question this decision to fly to Scotland from the outset, given also the certainty of the seriousness of the weather forecast
Not a bad choice but one made for no consideration to anything to do with flying and it is for this reason that the CAA should be investigating these events without sympathy.