Thanks VS.
Heavy bags dropping out could well induced by the a/c shaking violently, e.g. sev turb or even asymmetric slat, the first of which is certainly more probable than a crash I would have thought.
BTW, I am sure that I recall (last year or two) an airline using some kind of netting restraint in the overhead bins, in the last year or two, which was secured just before closing the lid.
Can't remember the carrier, but it struck me as a very good idea, if not a panacea for all evils.
Risk management is always a contentious matter, since there are may different agendas and risk attitudes, which is why I asked the question about the status of the bins, since if they are an airworthiness issue then aircraft should not be departing with limits exceeded, whereas if only advisory then the benefit-cost calculations come into play.
Having said that, I find it difficult to believe that UK airlines would fly in breach of airworthiness regulations.