Can anyone tell me where the thermostat is and how to change it?

 

The therm. isat the juction of the water pump and the engine block. You have to remove the waterpump to get at it. I've not done it on my rover but have on other cars. Can be a bit tricky depending onhow hard to reach some bolts and you have the serpentine belt to deal with too. the tesion has to be released.and you have to pay attention to how the belt comes off so that you can put it back on correctly. To the untrained like myself that can be a puzzle. Anyway once you get the pump off, the thermostat is a relativly inexpensive small part. Easy to pop the new one back in place. Pay attention to how the old one is facing so as to get the new one on correctly. Don't forget to purge the coolant system when its all back together. Check out the post below about thermostat for purging instructions.
There are lots of folks on this forum who can walk you through the whole process better than me but at least this answers you ? about where the thing is
Good luck
bc

 

Wrong, a D2's t/stat is located in the plastic housing located by the hoses on the left side of the radiator.
Why are you wanting to change it?

 

opps! sorry for the bum steer. Never worked on my disco 1 therm. Justassumed it was in the usual place. Should have known the brits would put it somewhere else
bc