Hope it's not the coolant - if it has oil in it, could be bad news - could mean oil leaching from engine into the coolant

Have you checked both oil and coolant to see if there is any visible contamination in either ? Look for frothing under oil filler cap and greyish gunge in radiator expansion tank. Dealer should be able to take samples for analysis - as if

Also what about power steering fluid (usually pinkish colour ?)
Where exactly was the fluid leaking from under the car ?
Might be worth getting it jacked up, cleaning everything down and trying to identify the spot where it's coming from. May mean not driving the car for a few days but probably worth it. Never heard much of porous VW engines but it has been a common fault in Porsche (early 996 and Boxster) and BMW's.
Not trying too be alarmist, but I'd want this sorted asap

Good luck and let's know the outcome.
Cass