In UK with a Verizon S3 and need to update to JB

[merskamp]

Long story short. I am in the UK with my USA phone for vacation. I cant get it to recognise UK Data network despite paying for the plan to do so.
Turns out I need JB update to get that feature for global data access.
I am now in UK and have ICS on phone.
I think the JB update is now available in US for the I-535.

I tried using Kies but it tells me:.
Your device's current firmware version is not supported to update via Kies

My phone is rooted but is otherwise a stock phone.

So how do I get this update? I cant do it OTA. I cant connect to Kies it seems to do it.
I tried going into Settings and software update and there is a 37 MEg download which apparently
takes the phone from LG1 to LG7 (I dont know what that means). I downloaded that over my wireless
connection but the phone says i wont be able to make calls for 4 minutes and reboots. However it turns back
on from the reboot in Clockwork mod and the install has failed. (That 37 megs seems too small for the JB update
so i have no idea.)
pdA:LG1 / pHONE:lg1 /csc:lg1 (vzw)

So help THe long and the short of it is I am in the UK wishing to recognise UK networks but have a US phone.
Help.

I am a bit of a novice with Android and would prefer not have to put a Mod on the phone, rooting was fine
but would like to keep software official as possible.

Thanks,
Simon

Cheers,
Simon