In my first-floor maisonette, post-war council build, the mains water supply has a joint main stopcock with adjoining properties, not just the one below. The stopcock to my own property is solid and, judging from the mangled mess caused by Mole grips, has been for some time. It now has a combo-boiler, so no tanks now. Fitting a new kitchen gives me the opportunity to start again but I want to minimise the time the water is off. I assume the mains-in is ½", given the age; would this be true? I understand that a modern 15mm stopcock with compression fittings will replace it directly; is this true? What is the exact spanner size for the old compression fitting and the old stopcock? I have a lot of Imperial AF and WW spanners, in addition to metric, but want to get the correct ones to avoid too much damage. Sideways photo!