Decades ago I read that for every 5mph over 50mph you loose 3 miles per gallon on consumption useage,
As at the time I had a company car and was paid an allowance per mile for fuel I tested this out in real terms (did 40k miles per yearly average then). I found that it was true and enabled a profit to be made on fuel allowance, sadly the coming of Fuel cards killed that income.
I have always kept that fact in mind when driving plus an hours batting along only gets you there a minute or two earlier, is time that critical?
Other fuel saving method is to try never to need to brake for roundabouts etc. by lifting off the accelerator around 800mtrs before. Braking generally means that energy/speed gained by burning fuel to attain has been miscalculated.
I would also agree with others that consumption improves after 10k miles and sometimes as much as 20k before the engine gives its best fuel usage rate.
Must admit that I was hoping for upper 30's from my forthcoming 204ps 4M DSG . I did get 35mpg from my Peugoet based Mobilehome even with a 2.5 tonnes box van on tow. Time will tell I guess.