Thanks for the reply Charlie32, I am also a GA pilot. It was drummed in to me during my training to prepare adequately before flight. Read the AICs, the relevant bits of the AIP, NOTAMS, etc, etc. As I am sure you do. Good airmanship dictates nothing less and is a healthy and professional attitude.
The purpose of the AIC was to give the users another method of warning, in addition to normal change notification. The normal means of notifying change is of course the AIRAC Amendments to the UK AIP, which come out a minimum of six weeks prior to any change. This is a process laid down in international AIS procedures, as well as being documented in the AIP. My expectations that pilots would have been taught this at some point in their flying careers is not too onerous I think. Each AIRAC change usually has a summary of changes at the beginning so that pilots can quickly glance and see what might affect them.
You make some relevant points about the focus of the new NOTAM system and I know this is being well covered by other GA PPRuNers in official capacities. Good luck to them. However it is a little bit of a red herring in this case since NOTAMS would not be used to advise users of the change in airspace which occurred. It is the AIP.
If our stray pilot had caused a near mid air ... or God forbid a mid air, in airspace in which he should not have been, I don't think the defence of not knowing about changes and lack of adequate briefing would stand up in court as a mitigation.
You have raised a very interesting subject though. Thanks.