An update, plumber visited this morning - we have 3 bar of pressure, but 4.5 litres/minute. Plumber suspects that the non-functioning stop-cock is actually partially closed, and that resolving that would see a sudden increase in flow.
However, the managing agent is refusing permission to turn the water off, which is required to change the dead stop-cock, and to fix a leak in the pipe (currently fixed using a bit of bicycle inner tube and a jubilee clamp).
Most stopcocks can just have the headgear swapped out making it a quick and simple job....no need for cutting out the old one etc.
Why are you bothering to ask the feckless managing agent...just get on and do it How can they "refuse"...it's essential maintainance...you have no water.
Us in the trade certainly don't have the time or inclination to deal with hopeless agents each time we have to shut off the water.