When I was buying a previous car (Skoda) the dealer talked me out of a diesel engine by explaining that they're not as cheap as they seem to be. You can get blinkered by the fuel economy & cheaper road tax, but when you factor in the more expensive purchase price, servicing & fuel costs, unless you're doing in excess of 30,000 miles per year a petrol is cheaper to run.
Not being one to believe dealers, I put together a spreadsheet with all the factors in (miles per year/fuel costs/servicing/ initial purhase cost etc) and found that for thr 8-10,000 miles I do, for this particular model it would take 14 years before I would see the cost benefits of the diesels mpg.
Since then I have always chosen petrol, but I do like the torque you get with a good diesel.