sorry for not getting back sooner, I have been at work today.
I agree with you that it must be an electrical problem as the warning is for oil level and not pressure. there are no noises from the car and it's performance is still good. The car is 3 years old and only has 19,000 miles so it is hardly even run-in.
It is not an intermitting problem as the light is permanently on.
everything you have suggested has already been tried or has now been tried.
I have asked my local garage to purchase a replacement sensor so I can eliminate the unit itself.
I was hoping it was down to a service light that could be reset on the cars computer, but it doesn't even show up on diagnostics.
I will let you know how I get on with replacing the sensor.
Thanks for now.