This was done on a Hymer B564 RHD 2002......but must be same for similar models of that era.
The blinds frame appears to be all attached from the side window cassette to the windscreen cassette/frame but I will show you how to remove cassette from windscreen. I assume will be reverse for LHD vehicles.There are are pics to show the steps......easier than explaining !!
From passenger side :
Removed inside plastic frame by taking plastic screw covers off then screws. Just slide frame cover out of the way to rest on door.
You will then see 3 little brackets supporting cassette frame ....remove these.
Next remove screws from cassette frame.
Remove upper blind guide rail located at top of windscreen (middle)which is a small bracket with 2 screws and releasing this allows you to remove guide frame side cassette. Note I only detached it from passenger side but could be fully detached .
The windscreen blind cassette is now loose and the upper blind guide on the side window can now be slid out of windscreen cassette. Note this will also come out of the side window blind cassette.
There is also a lower rail on passenger side which is also attached to windscreen cassette.....this also can be slid off easily.