After getting my shed broken into and losing all my tools, I bought the Asgard bike shed and now keep all my power tools, winter wheels and other stuff in it. I have had it 4 years now and am very happy with it and the tools stay dry.
Build a proper extension for it A mate's got one of those things, outside the front of the house, 'tis fine. (He also put a galv wall mounted single wheel holder thing up which is useful for holding the bike whilst faffing with the lock etc)
I'm going DIY and designing an upright locker for my roof terrace. If I had the space (and could hide the ugly fecker away) I'd probably have gone for one of those though.
Could you throw a few pics up please? I'm sceptical that you could get 4 bikes in but I want to be proven wrong because they look like the solution to my storage issues.