I have found a very suitable and cheap replacement fabric for the bunk beds in the Dormobile.
Actualy my wife thought about it. The 2 bunk beds in my Dormobile have a rip in it. I looked at Dormobile website and found they are £110

I happened to have a couple of stretchers lying around gathering dust.
This is the one. Cost about £11 in sale.

So this is the bunk before.

And this is the bubk after.

It is a nearly perfect fit. The fabric is just a cm too long, but it does hardly show once stretched. It is imho stronger fabric than the original from Dormobile.
Ok, mine happened to be black, but I think they do different colours and maybe different designs, maybe from different makes. You also need to adapt the fabric a little bit, undo the sewing on the top ends where the poles go in and sew a couple of stretches shut where the original poles slide into the fabric.
Very easy adaptation and very cheap in comparison with the original.
Maybe in time I will get the originals, but for now, the money is a bit tight, so this is a good alternative.
Michiel