Thanks - yes I found that one. It's nice and practical, although as you say for the wrong operating system. I did have a brief look for something similar, which is why I mentioned the config files, but couldn't find anything. It would probably just require some knowledge of the Ubuntu boot process.
There are two others which stand out in terms of their greater detail. Parts of them are clearly over my head, but both seem to lean in the same direction:
https://community.freescale.com/thread/312821
http://developer.ridgerun.com/wiki/i...Fi_Integration
The latter discusses such problems (and supposedly their solution although I can't see it) at the bottom of the page. I was hoping to take another look at it today but didn't get very far and I have a busy week ahead so I suspect I am just going to have to keep tinkering.