wow, i have a 53 plate 130ps mondeo too with exactly the same temp gauge problem, mine tends to work when its been moving for a bit.

as for the trip clock mine is showing 38.9mpg and ive worked it out with how much diesel to how many miles and it works out pretty much spot on (38.6mpg according to my calculations), many people have told me that the in car gauge misreads but mine seems to work spot on.