I did a round trip to Crawley yesterday which for me is 540 miles - mostly motorway but with the usual stop/start issues in the morning and the usual 'make progress' (ahem) opportunities in the evening. Tank ave going down was about 38 but I filled up at Crawley so the tank ave on return was for that trip - 42. Dead chuffed.
I have my aircon turned off - after a lifetime of company cars and co petrol i always just left it all on but I am convinced that it saved me a few mpg and it was no difference at all on the comfort. From now on I will only use it as actually needed. A couple of weeks ago my dealer did the dash padding refit and brackets following a squeaky central speaker and it is as quiet as a mouse.
So as i say - happy bunny.
As an aside - when they did the dash they lent me a 220d and i did around 200 miles in it - i reset the ave and, bearing in mind i am not used to manual i got 44 for what i would say was about 70% motorway. I see what you mean about the high 6 gear.