Alex Johnsons's Shedworking is "the only daily-updated guide to the lifestyles of homeworkers in sheds and shedlike atmospheres around the world." Not all of the sheds featured are prefab, but the UK site is still worth a look.
"The building is everything you'd expect from a timber flatpack (modular, customisable, portable, flat packed, renewable, recyclable, and with low emission materials) except it's built around a lightweight Smorgon stainless steel framework and PIR panels made from a fire-resistant urethane foam. It is, give or take a few cms, a 3m cube with adjustable legs and you can add modules together to make it bigger. A solar power system is optional."
By coincidence, I received an email from Alex while working on this post. I'll give him the last word:
"I also produce a bimonthly pdf magazine called The Shed for people who work in sheds and shedlike atmospheres. At the moment I am organising the first National Shed Week in the UK in collaboration with www.readersheds.co.uk."
(Hat tip: Future House Now featured a few models in a recent post.)