Thanks for the replies. I don't draw them up like a drawstring bag, what I've been doing is pulling the fleece over the top of the rail and stapling together. The replacement would be strings on either side of the fabric at the top and tying.
The fabric is unlikely to fade as it is north facing and rarely sees any sun in winter apart from maybe last thing at night on a good day, the house roof stops it hitting during the daytime.
Crazy quilting sounds like a perfect idea.
Can't use old sheets though, more recently they have all gone to the Sally Army and a tenant of a charity I am a trustee, he moved in with nothing so we all helped him out.
Problem solved.