G4 Conversion Question

Im wanting to Convert my EE UK H815 to an Open Europe G4. I can flash any KDZ, the Software version under > About Phone > Software Info> is always:

V10c-234-30 (I assume the "234.30" is EE UK).

Im wanting to Convert it to:

V10c.EUR.XX

Do I have to Unlock the Bootloader, then flash the Open Europe Rom.. to convert it.

Thanks