Are you looking to save cash or get a new car ?
Spending a few grand on a newer car to save £100 on insurance isn't going to make you richer
I'd have thought you get 40-45mpg all day long in your 1.2, especially in a long commute (assuming you're not sat at 110 all the way there !) - Lets say you get 55-60 in the diesel .. you've got 20% saving on fuel but it's 10% more expensive to start with.
Have you done your sums ?
If you need economy, dCi80 mk2 would be a simpler swap I'd have thought ? Lets say you get £2k for your car, and you pay 2-2.5 for a nice dCi .. It'll feel like a rocketship compared to your 1.2 too.
Much better on the wallet IMO
:evil: