get the petrol, the diesel is reeeeally front heavy handling wise and the engine is very rough and grumbly, plus its a huge amount more money compared to the low price of the car in the 1st place. I found the diesel very laggy, and ragging about in a fairly low mileage one I got 45mpg, not great, obviously would be better if I drove like a pensioner though. Our 1.2 petrol averages 53.5 mpg over mixed motoring, and is far more fun to drive.
Plus noone likes to use the black pump really do they! You get covered in diesel and everyone thinks you're cheap hehehe