hi all, Tonight while driving along my car started to drop it’s temperature on the gauge. It was fluctuating gradually down and then back up over the course of a 200 mile journey but didn’t make a noticeable difference in performance... It never dipped below 70 or raised above 90. No leaks or anything from the radiator. Is this the thermostat? If so how big a job is it? And how much would I be looking at for a garage to fit? It’s a 2007 3.0 TDi V6 (240bhp) engine. Thanks, Kevin.