Let me add my voice to those who say we should not speculate. The reports suggest the captain was very experienced. So many things could have gone wrong. Perhaps it is a small crumb of comfort for the families to know that the AAIB is the best in the world if it is possible to find out what caused this terrible thing to happen to their loved ones then the AAIB will most certainly find it.
My second point is that the comments about using R/T are in my view, important and not peripheral. I was flying in this area last week with plenty of showers, low cloud and bumpy air all over the region. Tuning into Scottish Info meant that I could build up a really good situational awareness of what was happening with the weather. I found out the altitudes and locations where some were having difficulty with icing, where zones of IMC were appearing all over southern and western scotland, and also who was going from where to where and which of them turned back and where. That, together with a quite superb service from Fisbang and his mates, who must of been tracking me by radar (else their Dead Reckoning is better than mine) made for a much less stressful journey back South. Radio isn't compulsory, but I would use it every single time.