With diversity you can lower the spec considerably for domestic, and anyone that listens to a builder or other non tradesman is an idiot.
Note; I already said the OP wouldn't need massive hot water storage, on the other hand I would expect someone that installs 2 or more cylinders to know how to plumb them up, including the primary and secondary circuits.
What the chances of 2 baths and 3-4 showers being used at the same time I have no idea, that information should come out in the planning stages.
So Alec to add your two penny's worth, what would you throw in the hat as best practice.
Note; I already said the OP wouldn't need massive hot water storage, on the other hand I would expect someone that installs 2 or more cylinders to know how to plumb them up, including the primary and secondary circuits.
What the chances of 2 baths and 3-4 showers being used at the same time I have no idea, that information should come out in the planning stages.
So Alec to add your two penny's worth, what would you throw in the hat as best practice.