Hi - I don't think I've mentioned the CAA?
sorry, I meant the AAIB
On your last point, the GA community could learn something from the military where each flight is required to be authorised - it can be self-authorised or more often done by someone else.
The process means you present your plan and someone else casts their eye over it and asks pertinent questions.
In this case, if he had phoned someone and briefly talked through his plan, you would like to think they would have asked questions about the weather and what he would do if it was bad en route.
It may be that he had done this sort of thing many times before and been lucky to get a cloudbreak or weather improvement - this is another classic human failing where the risks become normalised and he assumes he is a better pilot because he got through last time.