If I am not mistaken, the region codes are set up in the xRegistry.sys file.
There are various keys for Regioning and Languages such as:
/setting/bddvd/dvdRegionCode
/setting/bddvd/bdRegionCode
etc...
You can find an exhaustive list of keys with possible values for each key at
https://www.psdevwiki.com/ps3/XRegistry.sys
The xRegistry.sys file can be found with any decent file manager or via FTP at
/dev_flash2/etc/xRegistry.sys.
The keys can be edited with stoke25 xRegistry editor on PC, you should be able to download the app from our resources section.
They can also be edited with a webMan-MOD web command (check the wMM web commands thread's OP for the syntax) through any browser on your LAN or in PS3 browser.
Very soon, the PS3 Toolset will offer a fully fledged xRegistry editor directly in the PS3 browser.
Remember to reboot after an edit but always double check any edit you make before rebooting.
This is awesome information! I'll have to give this a shot this weekend when I have some time to tinker with the registry