Hi WMC,
I appreciate what you are trying to demonstrate with your table and for Mobility users it will be relatively accurate albeit in my area diesel is 5p more than petrol.
For private drivers it is a completely different picture once the higher cost of purchasing a diesel car, the higher servicing costs, the cheaper road tax, the higher cost of diesel are all factored together I seem to recall a diesel car was only cheaper to run if you were doing circa 20k miles per annum.