Provided they've been serviced regularly, you'd probably be better buying a high-mileage diesel than a low-mileage one. Diesels are best suited to regular motorway driving to clear the diesel particulate filter. I'd be worried about buying one with low miles that's mainly been used for local journeys around town. Bear in mind that a 10-year-old car with 75k on the clock will only have covered 7500 miles a year, which is pretty low. Out of your shortlist, the Octavia represents the best value for money.