In answer to my own question; after searching the US xbox.com site it appears the official xbox media remote is code based when it comes to programming it; that is if you have TV make xyz enter a certain code and limited functions such as on/off volume up/down will work.
However this is useless when I have deliberately aimed for 5.1 sound controlled by an amp, video switching is a necessity due to component input being on a different channel, volume contol needs to be through the amp.
What a waste of space the remote is. After I have invested in a HD TV, an amp, a Media Center PC and an Xbox 360 media extender, I find the official remote is not up to the job !
Obviuosly I have not bought each item for the particular purpose of using the 360 as a media extender but while I am now in this position, it would have been nice to have an official controller that could "control it".
I believe their is a logitech remote based on the harmony 525 released in the us that might be more suitable ? Has anyone experience of this ?