For that sort of mileage the fuel economy advantage of of diesel probably exceeds the disadvantages of maintaining its emissions equipment. If you will be driving 30,000 miles a year for 4 - 5 years then best to avoid the additional wearing components and additional fuel consumption of a four wheel drive. No reason not to run it on all weather tyres. Michelin Cross Climates are the best, giving excellent ride, steering feel and low noise as well as the benefits in winter. Avoid big wheels and low profile tyres. Go for 16-inch with 55 profile tyres.