Christian McArdle wrote:

This has been permanently plumbed in with two stopcocks right next
to each other. So I presumed this would be the way it fills. But,
when I open the valves, nothing happens.


That does sound like your filling loop, although it is supposed to also
incorporate a non-return valve and a detachable hose. Assuming you opened
both valves up fully, it sounds like either there is a 3rd valve hidden away
somewhere, the mains supply has been cut off, or one of the valves is
faulty.


The valves seem pretty good, they move easily, and one of them starts
dripping slightly when it opens, suggesting there is pressure there. I
don't think I'm missing a valve, I can see all the pipework, though it's
all behind cupboards so I guess I could be wrong. Don't think so though,
there's a hole cut in the cupboards to allow access to the valves and
nothing else like that in the house.

I wondered if I need to open the radiator bleed screws to aallow
filling, but if the pressure dropped as a result of bleeding the middle
level rad, that water would be replaced by the level dropping one the
top floor creating a degree of vacuum which should get filled when the
valves open.