no stopcock in flat above ...

Full bore is the key to not restricting the flow, just like the one you posted.

I would rather have one of these

Sparks...

Good thinking, I think there may definitely be room! How far does the lever come out from the joint (not when it rotates) - about 1 inch?

Emma

Probably 2 metered supplies with the meters located externally (?). There's usually an isolating valve in the meter chamber. Very many householders don't know where their stopcocks are located.

The message from "emma snipped-for-privacy@fastmail.fm" contains these words:

Hah! I lived in a row of three 1850s "cottages" in Hounslow which shared a common water supply. If you wanted to play with the pipes you had to go an ask Rene up at Number 2 if she'd turn it off for a while, but you also had to ask the family at Number 4 if they minded. The drains ran underneath each kitchen extension to a York stone slab in Rene's garden.

Anyway, I'd be tempted to use the one with a long lever handle instead of a little knob - easier to get a grip on when you're in a rush 'cos there's water coming out everywhere.

Strictly, I think you should have one of these

Depending on what the other person's like, they may prefer something like this

Would it have been difficult to branch off where the water entered your property so that one branch went through to number 4 and the other to an isolation valve feeding the rest of the property?

The message from Richard Conway contains these words:

Dunno. In the end the landlord paid for a new feed to our house from the road outside.

No meters. Just one stopcock in my cellar. He knows it's there, he just can't get at it!

Emma