I think I;m giving the enviromesh a go in favour of the fleece which blew away :)
I got some enviromesh a few years ago, forgot about it for a season (which at least lessened the shock of the cost!) and then used it last year to cover a fixed carrot frame which got trashed by the vandals last Christmas.
Rescued the mesh, a bit pulled in places where they'd stood on it which meant holes large enough for a carrot fly to get through. Didn't break though - it's very strong! Solved holes by doubling it up and using it as the cover for a Geoff Hamilton water pipe cloche over the carrots. V Pleased! No carrot fly!
I am tempted to get more of it so I can do it single-layer again and grow more carrots :) though if Tim's discovery is cheaper and finer I may look into that instead.
moonbells