Symptoms & cost of parts if you find you are going to require a replacement Water Pump. Some coolant loss over time. Only a very small loss over a few months. Then EML on dash and in limp mode.  Found to be faults relating to supercharger / boost pressure.   Supercharger clutch found to be defective. Clutch is built into water pump. (so new water pump & aux belt as this was not in great condition.) 03C121004JX Water pump  £156.39 03C121665  Seal ring           £4.70 03C145933A