I think that most European cars are built to run....and run fast and hard. Doing short drives is not good, stop and go traffic, etc...not good.
If you are not losing/using coolant...then no leaks I would say. Get a cooling system pressure tester from Snap-on or other and test it yourself. A cooling system pressure tester is a good investment and can be used on any car. Once you pressurize the system....you will find a leak if any.
When ever I buy a car, I always test the cooling system. Bad sellers pull tricks and change the coolant and oil, etc..