After the two posts about cases I thought I should probably let you know which one I got in the end...
I went for a Pibow from Pimoroni (http://www.pimoroni.com/). It's now available in more colours but I went for the original rainbow colours.
It's made out of 9 pieces of acrylic which are individually shaped to fit around the components of the Raspberry Pi. They are all joined together with a few plastic screws in each corner. The case gives full access to all the ports on the board and also has a gap for the ribbon cable for the GPIO socket.
Here's some photos of it: