Here, here - someone who knows what they are talking about.
The question was not ' how do I ensure I have hot water on tap at any time of day / night', it was ' how do I minimise my energy usage whilst getting the hot water I need at specific times'. Since the loss of energy is directly proportional to the temperature difference between the hot water temperature and the ambient temperature around it, times the length of time the temperature difference is held for, less energy is lost if one minimises this temperature difference until just before the hot water is actually required.