Just checked coolant and about 1cm below min, that's not enough to show a warning but it's lower than it should be! The handbook says any loss is usually a leak, but may be caused by coolant boiling off if it gets too hot. I can't remember the last time I checked it as it's always been ok until now, but obviously the car is only just over a year old. I've topped up with water and will continue to monitor. I spoke to Audi Assist who said they'd send someone out to have a look - but I said don't worry as it's getting dark, I'll call Audi tomorrow.
Has anyone else experienced coolant loss on a common rail TDI?