please fit anew sensor in the o/s door mirror ,it might be much cheaper  to get one of a scrap megane, at a renault  breakers  due to the fact they are not that cheap when you see what you get for your money , and if you are going to fit the sensor your self be carefull not to break the mirror and the outer cover ,once they are removed you just need to remove  the sensor and solder the new sensor onto the old wires.
                 mark
                
 May 2008