Hi we're currently down near tolouse, so first hand experience (mine is aMY19)
The manual says the headlights have a beam pattern that means you don't need to adjust or add deflectors.
There is an adjustment for auto high beam assist in the menu..
Believe my bulbs are LEDS so not replaceable, however I also have a spare bulb kit in my toolbox from my D4.
If you have the digital dash you can change to km/h.
If you have the speed limiter it's invaluable as they have changed speed limits in rural areas.
The adaptive cruise control seems far nore sensitive to cars exiting the autoroute so assume the forward looking cameras are calibrated for driving on the left.
There are speed cameras everywhere, much more than I have seen in previous years, I had the cruise set at 130 on the autoroute in good weather when I was overtaken by a Picasso who cant have been going much over 130 and he got flashed ,(blackvue showed I was doing 79mph so 127kph) so the tolerances seem very low. They have also introduced average speed cameras which seem mainly on downhill stretches.
Several of the toll booths had the gendarmes out in force , we were told they are clocking you as you come up to the toll booths and the speed limit drops and we're pulling over cars when they came out of the tolls.
If it's not too late get a toll tag, we've had one for years and they are invaluable.
Hadn't realised the breathalysers had an expiry date , last minute trip to Halfords was needed.
If you are getting the tunnel it was packed last Saturday , we ended up with a three hour delay and then they couldn't open the door when we got to Calais.
France has gone really expensive , £110 to fill up on the autoroute
Some of the driving is unbelievabley bad , again much more so than previous years,
Having said all that the D5 was a dream coming down , much more relaxed than the D4 and managed 38mpg down to the tunnel also hardly seen any D5,s
Hope above helps , enjoy your hols