My allotment was in need of a shed, my son had an old one in his garden almost completely buried under a hedge. My decision to rejuvenate it really paid off, old sheds never die.
It was roofless and unused for at least 20 years, I took it to pieces and patched up the floor. I got it to the allotment and added a new roof, windows and a few pieces in the sides. For the roof I used corrugated roofing material from Wickes, it is actually very thick felt and will last almost indefinately - it cost about £40. The door was rehung and the shed was given a couple of coats of preservative, it was already unrecognisable. Guttering would have cost about £70 but I got all mine from a reclaim yard for under £10, a Water butt and stand off ebay for £ 10.50 completed the picture. The aluminium box (I know is unsightly) was left on the allotment by the previous tenant, I keep it to store things that would mess up the shed. The shed inside is dry, clean and equipped with shelves, toolrack and a bench, a small gas stove provides my morning coffee.