Thanks, ***** ***** tried the temperature sensor connections and coolant level if fine. Engine is not really overheating. I have had a look at the temperature sensor and it measures around 2kOhms across the terminals which sounds about right to me. I am surprised that when the diagnostics reader is plugged in, no error is shown.
I have replaced the sensor and checked wiring as far back into the loom as possible but stilll the same problem.
I am suprised that an apparent high temperature (or a genuine one) stops the car from running, so I am tempted to think it is a deeper rooted problem.