UK Car Repair: temperature gauge, wire sensor, engine control module

Question
my 2005 astra 1.6 16valve cabriolet temperature gauge has stopped working although the engine temperature is fine , is this this sensor that has stopped working and if so where is it located on the vehicle so i can change it?

Answer
It could be the gauge, isn't the vehicle still covered by warranty?  I'm not sure where the sensor is, but on this car it is most likely connected via the main engine control module.  You could look for it on the engine close to the thermostat/outlet to the radiator. If there is a single wire sensor just short it to earth with the ignition on (not running) the gauge should go to maximum heat.