Engine coolant tank emptying

Hi All,

I have just purchased a mini cooper 05 a few months ago with around 55k on the clock. After having the car only 2 weeks the clutch went on the car and I have since had that replaced but I am now encountering a new issue with losing coolant from the engine coolant tank.

I took the car into a garage last Friday and they replaced the thermostat telling me that was the cause however the problem persists.

Does anyone have any ideas what is happening and what needs replacing? There is no white residue appearing and the car is not overheating so I'm hopeful it's not the head gasket.

Thanks, Joss.