Here you can find it for 30 GBP
This gadget made my XBMC work like a charm. This allows my Zotac miniPC to receive the keystrokes on my TV remote control, allowing me to use my normal remote to manage my computer.
Out of the box, it worked with no further config after installing the drivers provided. The default mapping of the remote was quite good (I did not find the need to customize it in a couple of months), but it can be fully customized to suit your need (here you have more information on this).
The best point of it? It has made my media center really simple to use... even my ganny know how to use it! No more need of other remote and (IMHO) much more elegant than having universal remotes...
Also, it is quite small and its powered by USB (image for reference, next to my wife's iPod and the included cables):