Having just read this very thorough report, have to agree with Crab here.
Firstly it is reasonable to assume the pilot did get disorientated in cloud. It also seems probable that for a number of reasons the R44's design made it more likely that either during, or when trying to recover from, such disorientation the catastophic blade-hits-tail failure occurred. But even if it hadn't, the chances of a fatal conclusion were high.
The real issue, as so often, was why the acft got in cloud at all, and why the pilot climbed. It is obviously not clear how this occurred, though from the presented information, I would have thought it a moderate, but not high, risk. The R44 had been flying at around 1500 ft, the cloudbase probably around 1600 ft, but the ground elevation was perhaps 600 ft in the narrow valley where he was initially flying, and 1000 - 1200 ft over the ridge to the west, beyond which was another, lower valley.
If this is all correct, he would not have needed to climb at all, even if he deliberately turned right (west) to either do a 180 or reach the other valley. Even the power lines on the side of the valley would have had an elevation of say 750 ft, so should have been well below. In fact, the pilot could have descended a couple of hundred feet and still maintained 100 - 200ft clearance over the ridge, which for someone used to measured risk and speed close to surroundings, should not have been an issue.
It maybe that a sense of needing 500 - 1000ft terrain clearance at all times pushed him into climbing into the cloud, but I find it hard to believe that.
Once in the cloud, his climb was alarmingly rapid - 1800 ft/min. Was this a deliberate, if panicky, effort to establish a sensible altitude before trying a 180 and descending? Possibly, though I'm not sure he would have climbed that high and certainly would not have allowed A/S to drop to 50 kts if he really knew what he was doing. Nor of course should he have turned at the same time, but then no-one could ever expect a pilot with such little experience to have much chance of putting into practice any theory he'd leant about IMC recovery. So it was probably all getting horribly messy quite soon.
But let's come back to this question of why did he climb in the first place. Of course, we don't know precisely what the weather was like, exactly where he was. It is quite possible the weather was locally much poorer, with very poor vis and considerably lower cloud. What does strike me as being interesting though is the fact that the turn appears to start just after G-OUEL had crossed the pylon line. Could the pilot have suddenly seen the pylons/wires in the murk and pulled up abruptly to avoid them, which caused him to enter the cloud, with the consequent partially/uncontrolled climb?
Whatever the sequence of precise events, this does emphasis yet again that inadvertent entry into IMC is a massive challenge to handle for a VFR pilot (and machine) and that it MUST be avoided at all costs. I've banged on about this before, and not to everyones agreement, but in this kind of typical situation, it can be avoided by simply going lower and slower until you either turn back, or just land.
NEVER loose sight of the ground.