Surprisingly, all the cars on your list have the same engine and in the price bracket you are talking you could be in for considerable expense replacing the diesel particulate filter and dual mass flywheel. So you buy a high mileage example because that's all you're going to get for £3k - £5k, then you have to spend £1,200 on a new dual mass flywheel and clutch, then £800 on a new diesel particulate filter and the economics of buying a diesel simply don't stack up. If the difference is between 40mpg from a petrol engine and 50mpg from a diesel engine at £6.50 a gallon and you are doing 18,000 miles a year you will be spending £2,925 on fuel for the petrol car and £2,340 for the diesel. So it will take you nearly 4 years savings on fuel to pay for the DMF and DPF, by which time you will probably need another of both.