As ever, there’s some total carp talked on this site.
Sure, the 1.6 Ford TDI is not a great unit, but neither is it made of cheese. Sad to hear that some people are having bad times, but “3 turbos since August” sounds to me like it’s a garage problem rather than anything else. There’s no engine on earth, not even a TVR one, that wears out as quickly as that.
My last ten cars have all been diesels. I never buy new, always buy high-mileage and have never, not once, had an engine problem with any of them. The cars include Audi, Mercedes, BMW, Ford x 2, Citroen x 2, Land Rover x 2, Volvo, Volkswagen….sure, there have been other problems, but I’ve not had a single engine-related issue. These are all high-mileage cars as well (the current fleet of Passat, XC90 and Discovery 3 have 400k miles between them), and have only ever been serviced when indicated by the car. They have the right grade of oil, I check the levels regularly, but other than that I don’t do anything special with them. I certainly don’t change the oil every 5000 miles, have special cooling down procedures or anything like that, though I never rag a car from cold.
Most unreliable cars in my experience? Saab 9-5 (petrol – turbo blew), Mitsubishi Shogun (my brother’s car – diesel – turbo blew), Ford Mondeo (petrol non-turbo – poor running from new – injection system never worked properly and spent week after week in the garage). Thing is, I know these are pretty reliable cars overall, just that personal misfortune can lead you to believe that the issues you face are endemic to the model or manufacturer.