I live in a flat built around 1930 (ie probably quite old pipework). There is a communal cold-water tank in the roof, but the shutoff valve in my flat doesn't want to turn. I've already called one plumber out who refused to touch it unless the tank in the roof was drained (which would be a nightmare to organise). Clearly I don't want to break the pipework and empty all the water out into the flats below me! I suspect he just didn't want to do the work (and assume the risk), rather than it not being possible.
Any tips or techniques for loosening/un-seizing the copper tap on the valve? The pipework looks in good order (although it's probably rather old), but I want to be as careful as I can be. As an alternative, a friend suggested freezing the pipe just above the valve, but I don't know how viable that is.
Thanks in advance,
Steve