Had the thermostat changed on my 1.9 cdti 120 today, due to it showing no temp on the dash, then rising to about 75 when in traffic and then dropping again. (Classic thermostat issues)
Economy has dropped, but the heaters have always got warm.+
However, even with the brand new thermostat is working fine, the temp gauge still isn't playing ball, and won't show temperatures.
I did have the dash replaced last year after it went pop, maybe I should pop it back to the dealers and see what happens there.