Thanks guys - a useful thread here. I too have 1.2 4x4 and have been wondering the same thing.
I drive nearly 50miles a day, some motorway, some town, and for fun, country lanes on way home (occasionally a short length of byway too for good measure!). Keeping to 65mph or less on motorway and gently on the other roads, the computer's average is 41mpg -- not bad, but the MJ would be better.
The road tax isn't really an issue. Take my typical 1000 miles a month, giving 12,000 miles a year. At 41mpg and at around £1.09 a litre, (if I've got the maths right) I'd use £1440 of petrol a year. With the MJ, assuming an average of 60mpg and diesel at £1.20 a litre, it would cost close to £1100 for fuel a year. By comparison, the £15 a year difference in road tax is nothing? But I'd save maybe £300-400 a year in fuel.
But then there's service costs? My diesel Multipla is exactly double the dealer's menu prices compared to the petrol version, and I suspect the same is true for the Panda. That could quickly wipe out the fuel cost saving?
The 'new car prices' for the Dynamic are £7595 for 1.2 and £8595 for MultiJet (Fiatsupasaver.com). I'd expect the difference between 1.2 and MultiJet 4x4 to be similar, so factor in that £1000 difference too, and the petrol isn't that bad after all. I think I'll hang on for a while before switching, personally...
Pete