Temp gauge not moving!

[twinxster]

Hi everyone, I have a problem with my temperature gauge, when i drive the gauge doesnt move. Plus the exhaust emission light is constantlly on.(has had a new EGR VALVE under warranty.) I drive 40 miles to work and the gauge doesnt move a millimeter. Only time it does move is when the car is stationary(after driving 40 miles) and then it creeps up to 75ish. The car is under warranty, so took it back to the garage(2nd time in 2 weeks,New egr valve plus the Alternator went last week!, but thats another story) and the garage put on a new temperature sensor. Car still the same. So had a look on this forum, and THERMOSTAT came up all the time. So i mentioned this to the garage yesterday, and they said theyd order the part in for me. Went there today to fix it(but garage was busy today and ill have to bring the car in next saturday) so they gave me the part to bring back with me next week to be fitted.(incase it gets lost or used on someone elses car they said) Ive added a photo of the part. Brand new from vauxhall/opel(it has a box with it) I want to know if were on the right track with this part. The garage has its own mechanic, but it took me to mention the thermostat, before they said anything. Is this the cure to my problem??? (I wouldnt take the car back there if it didnt have a 3month warranty on it, but fair play this is the 3rd part theyve given me EGR VALVE,ALTERNATOR,THERMOSTAT. Who knows, by the end of the 3 months i might have brand new everything under the bonnet.