I'm not a plumber, as just about anyone will tell in a minute.

Thermal Stores provide mains pressure hot water, by keeping a large amount
in a tank, and passing water through sophisticated heat exchangers.

In my house, which has a conventional fully pumped system, the radiator in
the bathroom is always on when the central heating is, I guess this is so
when the house reaches temperature the water has somewhere to go if one
of the zone valves fails.

It's occurred to me, that you could design a system which uses the radiators
as the thermal store. (Provided the pump was going.)

Has anyone done this?