I took to car electrician said either the sensor or cable or both......and the bumper has to come off.....now decide wether to pay BMW dealer 130euros plus vat for part and go through insurance to pay where I have to pay excess, or go direct to car electrician get part online and then get done without insurance

May be contact is green... I do not know why u went to electrican if u can check wrong sensor with your hand! Find wrong sensor and change it with the next one to be sure and that is it! And then go to bmw graveyard and get new sensor for about 30$ or from ebay!