I've just done around 1600 miles in 2 weeks in France in mw new A6 Avant and loved every minute of it.

Whilst there I had to carry spare bulbs and was trying to work out when the "middle" lights are for when xenons are fitted? I assume that they are full beam on non-xenon cars, but what about a car with xenons?

The reflector is used for the low power LED "daytime" lights, but there is also a bulb in the centre that NEVER seems to light up!! (dip/full beam, locking, engine on/off, etc).

Any ideas??

Did you try turning the high beams on and checking them?

And as the DRL only on Xenon equipped cars. RoW has the city light (minimums) there as well. Xenons now use the HID for low (dipped), high (main) beams and flash to pass functions.