"IMM" wrote in message
...

snip
First choices for a hosue should be:
- combi, or two combi's.
- heat bank (can combine the full kW/hr outputs of a boiler and the heat
banks stored water)

Assuming the mains pressure is adequate for the above.

Surely that is the point.
There must be a level of demand (mainly judged on house size and number of
bathrooms) which cannot be satisfied by the average mains water supply (and
possibly gas).