::

I doubt you could get one as robust as this for less than £20, already
made
up, I've seen them before, they just zip together:

http://snipurl.com/i5ge



We have one of these in the greenhouse as a sort of 'double glazing' thing
for the more delicate plants. However our neighbour have one outside!! Not
seen a winter through yet, BUT, we are South Coast Isle of Wight and do not
have tooooooooooooo much ttrouble with winters :-))

Mike