Good thread with valuable contributions. It has cleared up some issues in my mind. This information is not easily available to the line pilot and non standard practices seem to become established quickly in some airlines. My latest CAP 413 is pretty thin on the ground on these topics and appears to be aimed at PPL level.
While we are on this subject can anyone throw light on why crews from one or two UK airlines call " maintaining FL XXX " when they reach their assigned level, have already been radar identified and no change of frequency has taken place? UK controllers tend to respond with a polite "roger" but the response from a few European agencies is becoming less patient to these seemingly unecessary calls.