The default place to put/edit properties is the file messages.properties, which should be on the classpath.
No problems with seam finding the message file.
Looking for why the jsf standard errors seem to not play with seams inl8.
Anyhep on this apprecairted
Ok... Trust in the Seamsters....
I deleted the jsf file in the War src directory (where it's been living since year dot (and been happily working!)).
I rolled all my jsf overridden messages into the basic messages.properties (and the german version as I am supposed to setting up inl8).
Removed all the stuff out of both faces.config and component.xml to do with bundles/etc.
And it just worked.
I should have done this from the start! you got to love the seamsters boys...