You used to be able to buy a version with a fitting kit where you bolted through the roof and around the awning rail. Whilst this was practical it did not look particularly attractive. [to me anyway]
The latest version that is being fitted to new [post 2012] vans has mounting plates that are bonded to the roof. 24hrs later you can then fix the awning to these. Rose awnings in Dorset are the go-to supplier of these awnings and most owners have them supply and fit. It is about £1200 from memory.https://www.roseawnings.co.uk/
I have considered buying one on more than one occasion but shelved the idea on several grounds. They are expensive, the possibility of writing one off due to wind damage concerns me and if tempted to convert one to a "full" awning I think they are an expensive compromise.
Whilst they are undoubtedly good and have many happy users I like many have chosen to use an Isabella Shadow or Fiamma Caravanstore [I have one on the other side of the van permanently] for a sun shade, that are also surprisingly good at keeping the rain at bay.
The picture is our Isabella with a pair of Comfortz Sunshadz end panels from our recent trip to France. Over a 4 or 5 day period the rain was so heavy the river at the edge of our pitch rose 1.5-1.8 m. Whilst many owners had there sun shades sag and one collapse under the weight of water this held none and shed it perfectly down the inverted V.

Colin

P1060253-1600.jpg - Bild entfernt (keine Rechte)

The Caravanstore will still foul the door on the new post 2012 higher awning rail vans.There are ways around this such as bent spoons etc, but do you really want to take such a route. On the pre 2012 vans you could get around the problem by fitting a higher awning rail an extra 100mm above the existing one, but due to the different roof curve this is not really an option on the newer vans.
If you just want a canopy and are happy with the higher price you will not be dissapointed with the wind out. It's just that I'm a bit mean with some things so opted for the Isabella.

Colin