did you use a martindale tester?? did you get 3 lights on it ??if not then you have no supply to the face plate,do as sparky says,turn power off remove the screws that retain the face plate,check the wiring,if its ok,turn power on,put multi meter on volts,carefully check across the live and neutral,if you get no reading,check between the live and earth,if you get 240 volts,then you have a fault on the neutral side of the ring mains,check the circuit breaker that feeds the circuit,if you do get a reading of 240 volts,then you have a faulty switch on the face plate,replace it ,hope this helps ,be carefull when you work on a live circuit
mm
November 2012