Water in oil in Vauxhall Zafira 2-2 design auto.

I loose about a quater of a cup of water a month but have gunge forming under my oil filler cap as its still under a years waranty I took it back to my garage who said some water loss was acceptable and the gunge under the oil filler cap was just condesation with the oil, my waranty runs out in may, is the information they told me corect.