We retrofitted Edmund's car as he had removed his bumper to do the Xenon headlights. Removed the tank and bored a hole for the sensor to be fitted. Lead the wiring loom into the cabin, connected it to the control module and programmed the computer.
Presto, the Washer Reservoir Warning Sensor lights up during initial start up of the car and goes off if the level is sufficient. It would light up if the water level drops too low.