Just a quick update, I tested my reciever on friends car and worked fine so went with your idea Sierra and you were correct it was the wires between the BCU and the reciever even tho I was getting continuity between the 2 wires so checked for voltage drop to see if I was getting same reading at BCU as I was at the reciever and 1 wire I was getting same reading (battery voltage) and the other wire was significantly less so hard wired that in to test and central locking worked So traced that wire and found that at the connector in passenger footwell what I originally checked and cleaned actually had corrosion back down the wire so replaced rechecked and all working fine.

Thanks for all your help everyone much appreciated

Well done... that's why i dont like continuity tests made with a tool which works with 3 or 4.5V and no load