You could just ask your host to get their butts working for ya.
But if www owns the files, then www might be able to chown them.
This means you could try writing a script to chown your files.
If ur interested in trying yourself, check php.net/chown for example scripts.
Maybe joomlaexplorer could be of use (not sure it can chown?), or some backend that your hoster might have.. plesk, cpanel, that has a filebrowser.. this filebrowser is most probably also owned by www..
Good luck.