Our 1.6 TDCi did exactly what you describe from day one. Initially the dealer did not believe us but after I had taken the workshop manager out in the car for about an hour he agreed it was not normal. They then changed the stat and renewed the coolant which made no difference. Should be noted that the TDCi Fiesta loan car did not do this at all.

The dealer put in an enquiry to Ford Technical who confirmed they were investigating the issue and new parts would be designed. 5 years later when we sold the car it was still doing exactly the same and no new pars were ever fitted. But it should also be noted that the car always performed perfectly over those 5 years (other than that odd gauge issue) and the guy who bought it from us had it for another 7 with no issues (and he was a mechanic).

In retrospect if the car had lacked a temp gauge like my current motor I would have known nothing about it. Too much info is not always a good thing.