Thanks to those who gave feedback on my earlier questions / comments. Unlike the R44 seemingly flying in IMC for considerable time until it crashed, this one at least shows a rapid transition from VMC (poor though it is) into IMC. If I was a pilot, I would take a lesson from this footage.
Prompted by more recent posts, I have watched the video several more times: Earlier, I felt the helicopter was already descending as it approached ridge, but watching the lead-up again, I now feel the helicopter was instead approaching a very steep ridge from below or at best around same altitude as that ridge (pilot attempting to remain below the clouds?) so as it got closer the ground 'climbed' to the helicopter. Also, briefly from about 0:30, the sound from the rotor seems to become 'deeper'? Could this be sound of rotors beginning to stall as pilot desperately tried to gain more clearance passing over the ridge? Or am I trying to read too much into the audio?! As with Rotorbee, I also hear the 'clonk' (first tree strike) within a second before the horn activating at 0:41. Unlike 212man, I have a feeling I can hear the remnants of the rotors still thrashing through the trees as the helicopter falls between 0:43 to 0:46. Thereafter mainly the sound of the turbine winding down (would this have been the pilot shutting down?) and groans from those on board.