So yeah - over a year, it had become a bit of a running joke with the neighbours! Thanks to everyone who's chipped in with advice and encouragement! I probably wouldn't do it again, somewhat glad I did it though but next time I think I'd just stump up some cash for someone else to do the hard work (a lot quicker and probably with cheaper but still suitable materials). I gave up counting on the material cost after a while - it didn't grow much beyond where I got too but still it's a not a pretty number for what is just somewhere to store a couple of bikes and some gardening odds and ends.