I decided to check out the Fuel Consumption this weekend - Facts and figs as follows:-
Mileage - 490kms
re-fuel - 49 litres
10kms per litre = 44kms per gallon = 28 mpg
that includes sitting in a traffic queue for over an hour getting out of Tatton Park and the vast majority was motorway driving
TBH I am quite impressed with that as I usually get 22 - 25 during a normal week