This the article I was searching for. It is extremely detailed and very comprehensive.The main points are;
Statin Myopathies are much more common in the "real world" than in clinical trials , as people in trials are more carefully selected.
Myalgia can occur without a raise in CK levels.
Some patients may have underlying muscle disorders which statins further disrupt. My lovely mum died of motor neurone disease aged 80, but I know that this can arise spontaneously.
It may be a compromise between optimal LDL levels and toleration.