The 'plug and socket' thing mentioned sounds like the sensor that should be attached to the inside of the front bumper. I think the little fixing lugs on the sensor have snapped off mine? and thats why its hanging down! It won't fix securely to the locating hole in the bumper withot them.
the sensor isnt dear about £11 from vauxhall , but all the outside temp sensors are all the same from the cali to the vectra,omegas. so you could get one from a scrappie
no problem mate just hope i have helped a little , i used to work for a vauxhall dealership so i have lots of usless information like that in my head,lol
damian