I decided to use a 45 Gallon metal drum instead of plastic. I bought one on Ebay that had been used for something non-flammable, lined it with mylar, salvaged some PC fans and used a mains-powered drill and some sealant to knock out a basic growspace. I used a borrowed 125w CFL blue light with reflector as a base, added struts and hung 4 smaller CLF's during veg. I used rope & clothes pegs instead of yo-yos to adjust my lighting.
As the weeks have passed, I've been refining my build. Added little USB desk fans and installed two sealable 4" access holes, got myself an extraction set up. I tried some LEDs on the cheap that didn't work out, but I stuck with that idea. I put in a 3m length of cool white 5050 LED and invested in a 300W LED. Instead of a mass of cables powering up to 8 CFLs and the rest, I've now only got 2 plugs for lighting, 2 for extraction and the rest running off USB.
It's been great fun tinkering and modifying my first Space bucket and watching my crops grow well. Thanks to everyone in the community for their posts and their inspiration I've had great fun doing this!