John Rumm wrote:
Sometimes part of that was intentional, they might put the bathroom rad
in the gravity loop for the cylinder rather than as part of the heating
circuit.

I'd forgotten about that - there was a heated towel rail that always came on
when the hot water came on. Made the bathroom nice and warm. In summer we
used the immersion 'because it was cheaper' - that might have been a reason
why! (I very much doubt it was cheaper)

While the gravity might have meant the system would work without power, the
timer was electric so there was no way to operate it during power cuts. I
don't remember a pump for the central heating but I imagine there must have
been one.

Theo