You say that the builders took the supply off the mains before the stopcock. These were not builders, they were cowboy builders. Any feed off of your mains should be after the stopcock in your house, not before it. You need to turn off the water supply from your outside stopcock. You then need to put a new pipe after the stopcock and also a service valve on the supply pipe near to your machine so that you can turn the supply off after the machine has finished its cycle so that this doesn't happen again. If you can't do this yourself, get a local plumber to do it. You will also need to replace the solenoid valve as well, as this is where the problem started from.
Dave., July 2011