Well, changed the coolant sensor and have driven the 26 miles to work without a hitch.
In fact I'd say the engine seems to run smoother. Is this because the ECU actually knows what the engine temp is? Hoping for better fuel economy also.
I have a niggling feeling though that the thermostat is actually stuck open as on the motorway the temp needle never moved much over 50 degrees, and then in traffic started to creep up slowly.
Fan air temp coming into the cabin seemed to back-up the gauge readings as never felt more than warm on motorway, then getting hotter when stuck in traffic.
I thought the optimimum temp was the 90degrees mark but does it cause any issues driving it with the thermostat stuck open?