| My garage has confirmed the cylinder head as failed along with the water pump - appears I might have lost water circulation/coolant due to the failure of the pump and the rest is history as they say. The car had done 130,000 miles so it may be worth changing the pump if your Mini is approaching these sort of miles as a precautionary measure. When I think back to my company car days, the water pump was often the first thing to fail and usually around 100,000 miles! | 
