Correct Thermostat Housing

[mc_mini]

I recently had a coolant leak which was diagnosed as a cracked thermostat housing. The thermostat was also stuck open so both were replaced and coolant flush and refill done. All seemed to be okay for about a month but noticed last week that the level has dropped again. I topped it off and now it has gone down again. I have it booked in this week to try to diagnose an NCT emmisions fail and high oil usage. I'll get them to check the coolant leak too. Is there anything in particular that is problematic on the mini?

Also I noticed today that the thermostat housing has a green temperature sensor. I've read elsewhere that it should be brown as the temp spec was changed from 112c to 104c. Should I insist on having this part changed?

Car is a 2009 built Mini One 1.4 Petrol.