For £15,000 you'll be able to buy one of the best examples of either car. Both were designed to be reliable and economical. The 2CV will give you slightly more miles to the gallon that the Minor, I think it's 45mpg plays 38mpg on the official figures - but exactly how many miles to the gallon you get will depend on how you use it. If you're only planning to use the car for low mileages/high days an holidays you won't notice a huge difference. Mechanically, both are basic and simple to fix so it's the bodywork that will let you down - the Minor's 'Achilles heel' is its rear spring hanger because it is such a labour-intensive repair, but both models can rot anywhere. Parts supply is marginally better with the Morris Minor, but you're unlikely to struggle with either. And both owners' clubs are fantastic with busy social calendars and events to enjoy. If you're not sure which is for you, drive as many examples as possible.