^^ My mates 325d (being heavy with the hard top roof, not driving gingerly and runflats) always seems to average 44mpg for most stuff. That said, he never resets his trip so I'm sure its capable of 50mpg on a run if you were steady. In a saloon or coupe, with normal tyres, I reckon you could add 3/4mpg to that estimate at least with the Auto box, possibly more for the manual.
Around town he reckons he dips into high 30's.
Same engine as the 330d that Dave tuned in that video, just starts at 197hp. Even with GTI power, it absolutely pulls from a standing start and in gear with a nice smooth straight 6 sound. They are immense cars and I think next time a 330d would be top of my list when I've kept the A3 for a long time.