Hi All,
Bit late to the party on this one but just wanted to provide some more info.
I do 2 42 mile journeys every day and have had my car over a year(c300e). I can normally get over 100mpg on every journey and fill up to 100% on the battery every day . It costs me about £30 per month in electric(octopus intelligent go) and about £120 ish in petrol per month i get between 850 and 1000 miles for that. the below shows at 80mpg but i had done quote a few other +400 mile journeys to drop this down.