the dealers will charge you over 100 for a filter replacement. the filter should cost around £20 for the genuine ford one and it can be done in less than half an hour so i would go to a cheaper garage to get it replaced or change it yourself.
make sure that you or the garage fills the filter housing to the brim with diesel and you shouldnt have any issues starting it up
I wonder if it would be cheaper to just go for a full service. My car will be due for one this coming summer. Maybe I should book it in early as I am certain the fuel filter will be changed on a full service.