I reckon its the oil cooler, it went on mine, I was losing small amounts of coolant, nothing serious, no oil in water or water in oil but was leaking water out of the oil cooler, the diagnosis was to look at the cooler it sits just above the oil filter, it had collant crystals on it where the coolant was boiling off after it had leaked out, was covered in blue / white fur! when I had the system pressure checked by VW at the main dealer it didn't show up any leak at all!! was only using about 1/2 cup of water every 4/6 weeks so was not a big leak.
I changed it myself and it was a ba$tard to change!!
Mind you I only took off the oil filter and intercooler hoses and left everything else on the engine!!
Oh mine was a 55 plate as well if relevant