Back again temp gauge as shown in the picture but the radiator dosent get hot on the offside and normally the fans would kick in before the gauge got that high I am thinking thermostat would like more thoughts or ideas
bang your fist above the gauge, it can often tell lies and read high. if the pipe leading from the thermostat to rad is not hot when you know the car is up to temperature then the thermostat is stuck shut.
I changed the thermostat, fiddly but possible, when I got some strange readings. It did stop the gauge going off the scale at the top when cruising along in winter on a motorway at an indicated 65 MPH, but it still sometimes sits in the postion shown in your pic. I think its connections somewhere as the sender resistance measured good.