Thanks J and Rob,
I have taken your advice and have found the following,. Forgive me for sounding a bit thick but I'm not an electrician
1.) Oil float in remote tank checked with voltmeter to read resistance in ohms and the voltmeter set at 20k (not sure what that means) and at float position empty the resistance read 0.24 at empty and 0 when full. So I am happy with this and believe it works
2.) Oil float in reservoir is a different story and would not read any resistance at full or empty (submerised in oil and out of oil). I even tried the different settings on the voltmeter (2K, 200K, etc) and dead. Also the connection was very badly corroded and even when removing the connector and cleaning the end of the wires it made no difference. So I'm guessing that this is the problem and needs to be replaced? If it is any idea where I can get one from?
If it is the float switch this is because I removed the engine cowl (for security reasons) and put a plastic bag over it which had a hole in it