I think the Ford 1.6 tdci engine can give lots of problems

My neighbour had a Focus 1.6 tdci and scrapped it in the end

Guy I used to work with had lots of trouble with his also, for some reason the injectors go wrong, the oil carbons up, screws the turbo and bearings.

I'm just assuming that the Fiesta would have the same engine, would be worth checking though!