A bit like an airline pilot then. I suppose that is all in keeping with the biggles image that goes with the rest of the car. Must get myself one of those leather flying helmet thingies....and a spreadsheet!
I am happy to share my Full Spreadsheet with any takers. There maybe someone out there who could make it more dynamic as I need to adjust the formulas every Time I add fuel (when it recalculates average MPG)

Needs an email address though. (PM me if interested)