stop cock not working

Having disconnected washing machine for a new floor to be put down the on/off valve on the pipe which the wm hose connects to was not working so need to turn off mains to sort out. However stop cock under the sink turns in and out with no effect. Help! Is there anything that might be done to the stop cock to make it operational? If it has to be replaced how can this be done without the ability to turn off the mains?

Many thanks

Turn off the mains in the road?

hi,
if you cant turn the mains off in the road you need a plumber with a decent pipe freezer kit (not just a spray can from b&q)