Re: Hot & cold
1. You cover the header tank.
2. The combi-boiler has largely made this obsolete, for better or worse.
The tank may well still be there. It may have been put into the loft before the woodwork for the ceiling was completed and there's now no way to remove it. If, like me, you live on a hill close to the limits of the head of water in the mains* you realise that that local head of water would probably improve the shower performance if it were still available.
Then you have to take into account all the Canada geese on the reservoir, townies coming over in summer when the reservoir levels are low and letting their dogs crap below high water mark and similar.
* Any time they try to jack up the pressure at the PRV it causes bursts of the mains lower down.