The stop-cock replacement was made more complex with the realization that we can't disconnect the water for the whole block after all, because that stop-cock is also broken.
Turns out there are two water-inputs into my flat. The mains connection plus also a tank in the roof.
Nobody seemed to want to explain why. Something to do with pressure maybe. But if mains-pressure can fill the tank in the roof can't it also blast my shower?
Anyway, both inputs to the flat have broken stop-cocks, plus the one that feeds the whole block is broken. How do you deal with that?
The mains-input stock-cock does actually just-about work if you get enough leverage on it that you nearly break the pipe. So they can close that one, add a new tap after it, turn turn it back on. Now I have two stop-cocks there and only one is broken.
I think with the other one they drained the entire tank then replaced the tap live when it was down to a drip, something like that. I was mostly working. Dunno what was going on. Splashing and swearing.
Heroes frankly, I was suspecting there'd be months of delays while the bankrupt Thames Water postponed replacing the block's stop-cock.