Exactly....I'd just add that if I do 70, to overtake people doing 60 without holding up people in the middle lane I need to put my foot down....EATING fuel.
Hmmm , but how can you be 'holding up' anyone if you are already travelling at the MAXIMUM permitted speed - following traffic is just NOT ALLOWED to go any faster .
I just recently drove the road under discussion en route from Glasgow to Kent and had no difficulty in maintaining a steady 70 most of the way ( achieving over 60 mpg in a Diesel Golf , averaged over the round trip ) . Most of the time I remained in lane 1 , moving into lane 2 as required and only occasionally needing to use lane 3 . I don't see the problem .