"David Hansen" wrote in message
...

The main source of hot water is best situated near the tap that is
used the most, usually the kitchen one. If the other rooms that have
hot water are clustered tightly around this, horizontally or
vertically, then that minimises losses.

If gaining space is the aim then put the combi or water store. when
convenient and install a DHW secondary circulation loop. Lag 'all' DHW
draw-off pipes.