I've just realised I've had this car a year now so I thought I'd summarise how this generation of hybrid tech does.
In a nutshell, it does 29 miles on a charge in summer and a low of 23 in the winter. Having heater/lights etc makes a lot less difference than you'd think, but preheating the car before setting off (while plugged in) will knock 5-8 miles off the range. Once the battery is depleted, I get around 40 mpg, though this can rise to almost 50 on the motorway, where the regen tends to have more of an impact.
I'm the perfect use case for this car as my normal place of work is exactly 12 miles away, meaning that I can often run Mon-Fri on electric power only, with the rest of my mileage being almost entirely motorway. My cost per mile has been significantly below my previous diesel and hugely less than the petrol, though this has not been exactly a normal year.
So far, been worth it financially, even without the massive tax break. Utterly forgettable car though, I hope to never own another BMW or Audi again, unless I can find a nice nick E39 or relive my younger days with an E46 M3.