So reading through that report and the others from the AAIB so far. My understanding is as follows:-
The aircraft shouldn't have been flying at all (airshow or otherwise) as the maintenance organisation had effectively mis-declared that the aircraft was fit to fly as it had out of date items and therefore should not have had a renewed permit.
The Pilot should not have been given a DA by his mate in the team. As both broke the PtF by displaying/flying over congested areas and the conflict in interest.
The FDD had not complied with CAP403 correctly either as no risk assessment for this aircraft had been carried out.
But until the final report is made we are still non the wiser as to cause of the crash, just that there were at least 3 reasons the jet shouldn't have been there.