redirecting sub-site urls


I have set up a wordpress multisite marketpress website and originally directed my wordpress site to with all subsites being this url http://www.byronmarketsonline/sitename

I have now changed the main url to, this was always pointing to the same site, but now I would like this to be the url for all subsites

Is there any easy way to do this, the instructions I have found on this explain that multsite relocation of url is difficult and no instructions how to do, but I am wondering if there might be a loop whole as the main site directs to both urls, is there a way to simply change the urls of the subsite to add the additional '.au'