Having read this thread I checked my engine late last week and have rust on the surface on both pipes (doesn't look to have gone deep at the moment. I took the car to my local Ford dealer for them to take a look and they said they were unaware of any issues and had never seen anything like it on an Ecoboost before. Their initial advice was to "keep an eye on it" but when I made my concern more clear the recommended rubbing the surfaces clean of rust and to apply some VHT paint to prevent further corrosion. I'll be sending an email to Ford UK to get their view on the problem, and I'll include these pics together with the link to the Danish info posted earlier. Given what appears to be a low number of cases I won't hold my breath for a positive response. The car has done 45k and has had 4 services since new.