".for 2 u-shaped bits of metal and a plastic bar, then? There's no height or angle adjustment, which makes it an ergonomic no-no as far as I'm concerned. Kensington do it better - for a few quid more, you get full height and angle adjustment, and a 4-port USB2 hub.
Why would you need to adjust the angle? You should never be using the keyboard when you have a laptop on such a stand because that makes the keyboard too high. You need an external keyboard and mouse to use it properly.
That said, you should be able to adjust the height, as you definatly can't stack them.
IBM thinkpad users wont think much of it either, getting your thinkpad dock on the top of that won't work too well.
I do agree though, £30 is a bit steep.