Comfort zone
Having followed all of this from the accident day I feel that whatever the reason for this tragedy the pilot felt he was well within his capabilities with regard to the weather conditions prevailing.
As others have said this is the nature of the beast. Helicopters fly into places that the fixed wing can't reach. Very seldom do they slide down an ILS to destination. From my (ground based) observations they're often aloft in marginal VMC weather. He wisely aborted his first destination and was probably still thinking of the closest diversion to Elstree so as to inconvenience his passengers the least. This was after all, a commercial operation.
He wasn't even close to throwing all away in a life/death situation and landing in a park (for chrissakes). That really would be a career terminator. This was a weather diversion well within the remit of a professional. With his experience he would've aborted that diversion/destination too if he thought the weather beyond his capabilities which we must presume he didn't. For reasons yet to be determined his judgement was in error and he flew into a girt big crane perched atop a girt big building bloody close to his track. Cut the guy some slack, we've all nearly been there.