It is 7 years since we had a car with that engine, so I'm just guessing - is it the plastic maybe thermostat housing that has become distorted or cracked and is now leaking coolant?
VW Group cars, up to the present time have a history of failures in that area due to plastic mouldings distorting and or cracking!
Although on both the 2002 VW Polo owned from new until it was 13 years/105K miles old, and the late 2009
SEAT Ibiza owned for 10 years and 65K miles, this did not "happen" to them.