Hi Paddy,
Yeah - in the end I came up with the optimal solution to the square closet in a workroom problem. I bought one of those tall wheeled mechanics toolchests/cabinets (330x700x1300) that have a large section in the bottom and a series of different sized drawers. It's just less than half the width of the closet and a bit shorter. Mine also came with a seperate top section with handles. Its the 13 drawer toolchest on machinemart. It was a bit topheavy, so I've been ballasting the bottom with as much as I can in fear a geek friend in the ferrety raptures of science might inadvertantly tip it.
The closet previously had suboptimal shelves, so I cut these all in half. The toolchest with all my bolts/nuts/rivets/zipties and other cosumables slides in there when not in use. When I'm working I wheel it out so its behind my workbench (which contains my tools). This pretty much creates an ideal solution that packs away neatly. That way my tools and worktop are in front of me, and my consumables are behind me :)
The remaining shelves are used for a series of large cardboard boxes/bins containing bulk comsumable, materials, odd mechanisms, specialist project boxes, and bits and bobs. Whats nice is that when the toolchest is not in there you can just walk into the closet and peruse happily. :)
Now I just need to work out some sort of system for storing the wood and metal bar/sheet/plate/tube.
It's not the most exciting of hacks but if anyone is interested I can post a pic or two :)