We,ve used shower curtains in place of a full safari room for a while now Jan. Rather than hang them upside down I slide them on to the end support bars of the awning, then with the windbreak in place simply clip them to the w/b poles. This covers the two sides of the awning and the front is done the same but with a old cut down windbreak that can easily be stepped over.
We use plain blue curtains that match the graphics on the van and w/bs, and the beauty of this is that they are cheap, lightweight, can easily be tied back and easy to put up and down, which is ideal for us where one night stopovers are the norm. Not perfect I know, but for a outlay of less than £40, compared to £500 plus for the official version, something thats easy to live with.