I managed to replace the sensor, probably took about 10/15 minutes. But it hasn't solved my problem.
This is how I fitted the sensor, I'm pretty sure this is how the old one was fitted but wanted to make sure...

Same symptoms as before, stood in traffic the temp will sometimes drop, setting off and travelling between 20mph and 35mph the temp dial reads 90c anything above those speeds and the temperature increases. I was doing 55mph down a hill this morning, I think the revs were less than 2k (in 5th) yet the temperature was increasing. Even though the temp will go up to the red on the dial the fan never comes on.
I've read the thermostat is a fairly big job? I was thinking I could try and change that and whilst I was at it have a feel for the water pump? Or shall I just book it in to a garage?