the coolant temp sensor is part of the thermostat housing so this is why the fan is permanently on
a genuine thermostat is about £70 plus anti-freeze ( £20) plus an hours labour to change so I can see why they're quoting £180
you can get a pattern part thermostat housing ( they are electrically heated , so cost a bit more than regular mechanical items) for £55
do you still need help?
Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you