Fast forward a few weeks, and I am in England with an Orange sim in my phone. I have no problems with voice, but I cannot access any data services (I have no trouble receiving texts, but cannot send them - I think this is a problem with the sim though). After searching around the internet for a while, it seems that the solution to my problem would be to add the Orange APN settings to my phone.
HOWEVER, Verizon's version of 4.1.1 does not allow you to edit APN settings! When you go to the APN menu, there is nothing displayed and the only settings option is to Reset to Default.
The closest thing I've found to a solution is here, but it's a bit out of date as the method isn't for 4.1.1. I'm a bit wary of rooting my phone and installing a rom, as I've never done anything like that before.
Does anyone have any experience with this sort of thing that might be able to offer a solution? I would be willing to root my phone if necessary, but I'd need to be directed to a pretty explicit noob guide for doing that