Oil pressure buzzer and LED keep coming on at speed

Hi
  I have a VDO gauge in the consol so I know the pressure is good,  but the dash oil psi light and buzzer keep coming on, every drive at speed ,for a longish duration.
  Help please , i've checked the conections under the bonnet , but shall I change the sender above the filter ?, how can I check it to be faulty.
   I also have a sender on the right of the cylinder head for the vdo gauge.

 I'm thinking the conection directly above the oil filter is for the pressure as well as the one on the cylinder head . Why is there two ?.
          Thanks for any views on this
                       Ali

I know how you must feel… Mine is the same and I'ts driving me mad. Is there a way of disconnecting the buzzer from the clocks? as I have most of my dash of at the moment.
HELP PLEASE!!!!!!!!!!!
Gary.

We ought to start a club. The golf buzzer mental heads. I feel like doing a basil fawlty on mine and whacking it with a tree branch. Make it stop....pleeeezzzee

My oil pressure light has also come on with the rev counter needle hitting 120mph on start up. I've noticed that if I knock the clocks with my knuckle the problem goes away. I'm going to hook out the clocks at the weekend and give it a good going over. The outside temp is also reading -31 and the MPG is reading 99.9