Disappointing mpg on modern diesel Audi

The car: Audi A4 Avant, B9, 35 TDI, 19 plate.

600 motorway miles driven at the weekend:

  • 300 miles north - 47 mpg
  • 300 miles south - 54 mpg
    • I can only put the difference down to some traffic and bad weather

I was hoping for more out of this Audi. I had a 2007 A4 2.0 TDI that would easily hit 60+ mpg without trying. For 54mpg on this car I was trying.

The car is completely stock. Do these numbers sound surprising to anyone else, or as expected? Is there anything I can do to improve these numbers? Thanks!