Bladecrack, thanks for the insight on training.
Pete: the question of how the aircraft ended up with the rotors not turning before it made contact with pub roof was raised early in this discussion -- pages and pages ago. It was triggered by initial info from AAIB.
That factor eventually evolved into the split to that stand alone autorotation thread during which you introduced yourself to the membership at PPRuNe.
We need not ressurrect that, it's already in the thread.
A provisional conclusion that the pilot (RIP, Dave) was surprised by both engines failing is probably valid. With the extensive explanation of EC-135 fuel system features provided by some folks here, it seems that one would expect fuel starvation to hit one engine before the other: failure in serial, not on parallel.
If in this case that didn't happen, and both dropped off at the same time, the surprise factor / startle factor seems almost certain.