The switch for the washers is in the "earth" side of the circuit. There is a ignition live via fuse F36 to one side of the pump and the other side goes to earth via the stalk switch.
Check the wires to the pump as one of them shorting to chassis will make the pump run all the time the ignition is on. Check where the wires go down the hole with the washer bottle filler spout and also around the stalk switch.