me here again
forgot to mention that the oil pressure switch ( for the dashboard light) is also in the same vicinity, so don't get them confused. The oil pressure switch is grey& black and has a 22mm nut for removal, the temp switch is 12.5mm nut, and brass in colour. You can test the temp sender easily as it resistance chages with temperature, so using a multimeter and a mug of tea ( or hot water), you can see where the fault is.
It also helps visibility to remove the plastic covers over the engine and fanbelt - they are both easy to shift, and also allow the fanbelt to be checked.