Firstly, somebody (Aerbabe?) posted a link to a site with instructions for making your own in the last year, anybody know where it is?, it's eluding me.
Secondly, if you can spare a day (and also you get a free look around the museum at Duxford), go to helitech
next month. I'm pretty certain that I recall a few companies selling temporary hangar "solutions" at the last one. The big advantage of this (apart from the free look around the museum!) is that you get to actually see them up.