A valid point, although any engine running with a pump that doesnt circulate will almost definitely overheat. Being as the Temp sender is in the cylinder head on these i would have doubts as to whether this would be the fault in this case.

My car runs exceptionally cool but even in this bitterly cold winter the heaters are still toasty warm and the gauge sits up in the normal section, and im only running a standard lump too! Dont mean to sound patronising - you sure you fitted the stat the right way round and that you clipped it in securely? The clip is a bit of a nightmare to fit properly.