...gauge is only showing 70 degrees c? I have taken it back to the garage and they say its ok, but it was running at 90. but they have changed the thermostat and there is no change, its taking anything from 7+ miles to get up to 80 degrees C.Went for a ride out 14 miles and it still was at 80. Its only done 1500 miles. he said it runs better when its colder. is he right. i don't think so.

The outside air temperature is low at the moment around freezing point so the natural cooling air is colder and your vehicle would take longer to warm up,The thermostat could have been stuck open but as you say they changed that and your electric fan if you have one shouldnt be on,if you hear it on at 70 degrees then the thermostatic fan switch is faulty.Around 80 degrees is normal for this cold spell though