Unless you will be doing well over 15,000 miles a year it makes much more sense to go for one of the new small petrol turbo engines such as Peugeot/Citroen's 1.2THP 130 that has bags of torque (230Nm) and in my hands averaged 48mpg over 12,000 miles. Yes, diesel residuals are dropping already as the public becomes increasingly aware of the high cost of maintaining the emissions kit they now have to have: EGRs, DPFs, etc.