Update:

I've basically got the plugin system working along with a xhtml plugin. 
However there is one problem - KTrader doesn't like colons in the query when 
I use the namespace uri. Is there a way to escape it? (I'm simply stripping 
them out at the moment).

Secondly, is it OK for me to create a branch so I can keep track of what I'm 
doing?

Thanks, Paul.