Trouble unlocking SE W850i

Hey, newbie here.

I have had some trouble unlocking my W850i for use abroad (outside the UK) after flashing it with XS++ using the following files from this site:
- W850_R1ED001_MAIN_GENERIC_CY_RED52.mbn
- W850_R1ED001_FS_T_MOB_INT_B_RED52.fbn
and in XS++ itself I selected the option to use
- Custpack: EUROPE_1 (CDA102568/10)

When I insert a different SIM card I'm told that the the incorrect SIM is inserted and looking in the service menu (>*<<*<*) under 'Service Info' - 'SIM lock' it shows a series of padlocks (where [U] is unlocked and [L] is locked) as follows:

Network [U] 5
Network subset [U] 5
Service provider [U] 5
Corporate [U] 5
Extended [L] 5

Can anyone help me? I'm assuming I need to unlock the "extended" service, but I have no idea what this is or how I can do it.

Many thanks
DanJam89