Looking at the UK visual flight rules in section 4, outside controlled airspace, how long has this helicopter provision been in effect?
At least 4 decades to my certain knowledge. Quite probably more?
This is the fundamental difference between helicopters and fixed wing. It can be, and frequently is, perfectly safe to fly in weather so marginal that ONLY entry into IMC prevents flight in accordance with VFR! Not the case in a fixed wing!!
The underlying principle is that the ONLY back up is an immediate IFR climb above safety altitude, or an immediate landing. If one is unable due icing, or unqualified, to confidently conduct BOTH an IFR climb, and subsequent instrument recovery to a suitable diversion, then ONLY an immediate landing remains!
However, if at the same time, the terrain over which you are flying is not suitable for a landing, then your options have disappeared. Tragically the result is then inevitable.
I say again. I have no idea what the cause of this accident was. It's simply too early to say. Unless there are recorders onboard the aircraft we may never know with any certainty. Investigators may just have to collect what physical evidence there is, and make an informed guess. Very, very sad for those left behind, but a distinctly possible outcome.