I have just tried it with my new locked to orange g600 and it works fine on all networks.
1-Turn on the phone without sim card .
2-Pull off the battery cover and insert any non-accepted sim card (without turning off the handset)
3-Do full reset *2767*3855# , phone will reboot and goes to Menu .
4-Customize Sp-lock code *7465625*638*00000000*00000000#
5-Unlock your phone with new SP code #7465625*638*00000000#
6-Enjoy G600 unlocked
Not sure if I should have posted it here or in misc so feel free to move it if need be.