What may have happened is that while running the engine at high revs(MOT test?) without big fan in front of the radiator, they caused it to overheat and it dumped coolant from the plastic coolant tank .Suggest you check the coolant tank cap - a notorious weak point. make sure any replacement is the latest upgraded part number xxxxx004 I think but confirm. The coolant tanks themselves are weak and refilling is a bit of a process.
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