Since having a water pump replaced on my car (and a coolant system flush) I've driven about 50 miles and the coolant in the header tank now has a fair amount of the brown scum in it!
The coolant level looks to be down, but it doesn't seem to be losing oil, and there is no mayonaise effect in the oil filler or cap.
A leak is apparent on the lower left of the engine and a garage that looked at it the other day was quite keen to replace the head gasket.
The temperature has never wavered from the fraction below half way that it hits after about 10 mins driving, and I haven't experienced any power loss.
Now, could this be the inlet manifold gasket? I don't mind the garage changing this first as its cheaper, but they seem to be very keen to go the whole hog and change everything with a £350 price tag.
To recap I'm really only getting coolant contamination.