Just to add what I know about the systems:
The AIMS and FADECs are only linked at the throttle levers, AIMS drives servos and resolvers determine the angle selected for the FADEC thrust setting.
The FADECs on the B777, R-R engines are NOT programmed in ADA - most of the rest of the plane is, true, but not those particular items.
The teams that developed the software for the FADEC are VERY experienced professionals who have had safety-critical training. Not that we can't make mistakes just the same, just not very likely.
(anyone spot the 'we' there - oh, what a give away!!!)
I am not second guessing the AAIB, I will leave that to the PPRUNE massive, who seem to have attracted even more speculators than a gold-rush. And, I do post there too, trying to keep the arguements to the facts, though it's an uphill struggle.
at which point, pass my anorak and show me the door