So drove about 10 miles today into town and whatnot, went to change the driveshaft on the missus' 306 and noticed a small puddle under my A4...
Had the pink tinge like the coolant and sure enough the level was just under the Min mark.
Let it cool for a few hours, jacked it up, popped the under tray off and started up but no obvious pipes leaked at all. Loosened the header tank cap and there seemed to be a fair amount of pressure built up in only 10-15 mins (hadn't even warmed to 90°) and it spooged some coolant again, leaking into the same place it appeared to have leaked from before judging by the marks on the undertray.
So, headgasket on the way?