Hoorah! I replaced the temperature sensor this evening and went for a drive and had no problems whatsoever, I'll see how it fairs on the commute to work tomorrow.
ripped my arm to shreds getting the plug off the back of the sensor though, it was caked in coolant, also inside the plug was full of dried coolant and the o-ring was ripped too. I cleaned the plug out, replaced the sensor and its hopefully sorted now.
photos of older sensor attached.
many thanks
matthew