On 10/10/2018 22:11, TimW wrote:

existing valve is blocked or not or if it's fixable. I can go to mole
valley or somewhere and buy a new ball valve or similar no problem, but
lets say I cut the pipe with a hand saw and water gushes out.

You should turn off your own water and see if that stops it, then turn
off the neighbour's. You need to know where the supply comes from.

Bill