it came down much faster than it would've done had the pilot been able to glide it
from witness reports inside the pub, it seems to have been a 2 stage event, with the heli ending up the roof with more control than just gravity, followed shortly after by the wooden roof collapsing under the weight. So providing these witness reports are factual, some level of auto-rotation control was still possible. Pure gravity would have smashed right through the ceiling.