Regarding the fuel, there are some details, along with some discussions of operating temperature, in the Wikipedia page: http://en.wikipedia.org/wiki/Winter_diesel_fuel. The temperature ranges suggest that you're unlikely to have serious issues with your diesel car, if you buy fuel appropriate for the season. The inconvenience factor of owning a diesel car compared to a petrol one is pretty minimal, as far as the sort of cold weather that most people who might consider buying a car (as opposed to something with tracks, skis, or 4' tyres) will generally encounter.