OK..Step by Step: (OS X)
Assuming you have already downloaded Boxee.
1) Visit
http://code.google.com/p/xbmc-iplayer/ and download the plugin
2) Open the Boxee Package contents and browse to:
Contents\Resources\boxee\plugins\video
Create a folder called iPlayer and copy the contents of the downloaded plugin to that directory
3) browse to ~/Library/Application Support/BOXEE/UserData/profiles/
chatterbox/ and open in TextEdit
sources.xml
4) Under the Video section add:
Code:
<source>
<name>iPlayer</name>
<path>plugin://video/iPlayer/</path>
<private>false</private>
</source>
5) Launch Boxee, go to Video, Internet Video, Select iPlayer
6) Select the Channel
7) Select the Program
8) Select info
9) Press Enter (there doesn't seem to be a button but it just magically plays)
Taaa Bloody Daaa
PS - Thanks to Clarkee for some pointers 50/50 me ol' mucker