Welcome to the club, Ken.
The 2.7 diesel engine is a rather good one, and with a good mileage on long runs. I have an S type with the same engine and on an 90 mile run I got 50.2 mpg on a motorway with road works and 46 mpg on the return trip on a motorway without road works,
The petrol engine is a good one but will not have the same mpg, but will have good shorter journeys.
Regards,
Peter.