My oil light is not working when I switch the igintion on before starting. I followed the instructions in the manual which state, check the bulb (Ok), take off the earth to the oil sensor and earth it out on the crankcase, it should illuminate (yes it did) So do I take it that the oil sensor in the engine is shot?

 

Sounds like it could be. if the bulbs works when you run it straight than might be the sensor its self.