I have the " Low Washer Fluid Level " sign showing I have filled it up but nothing changes Does anyone know where the sensor is ?

 

I seem to remember that it is a small magnetic float switch mounted on the washer tank, if you look from underneath the car you may be able to see the elec connections to it.
it may be near the pump, cant be more sure as it was years ago on my first s type that I had washer pump problems on, I do remember having to take of the splash guard fixings to bend the guard out of the way to access it