well that all depends. if you look at your mains, they are all:
W580_R6CA001_MAIN_ORANGE_LA_RED52
W580_R6BC002_MAIN_ORANGE_LA_RED52
W580_R6BA020_MAIN_GENERIC_LA_RED52
W580_R8BA024_MAIN_GENERIC_LA_RED52
W580_R6BC002_MAIN_GENERIC_LA_RED52
W580_R6BC002_MAIN_GENERIC_LA_RED52

I would use the MAIN_GENERIC. Its generic and can be used with basically whatever (except chinese language). now if you look at all the names of the MAIN_GENERIC firmwares, they look the same except for one section. (ie R8BA024 on the second MAIN_GENERIC) this is the firmware version. It must match the same firmware version as your FS. If you no exactly what languages you want, you can look here and choose the FS that contains the language that you want. You then just need to make sure that you use a FS with that same Firmware version that you chose for the MAIN_GENERIC (or other way around dosen't matter. You just gotta make sure they are the same firmware version). You then just need to look here and match the right custpack to what your using and there you have it. Thats how you no. Just flash them all and your phone is ready to go! Now even though you live in the UK, you can use any MAIN, FS, and custpack you want. You just gotta make sure you choose the FS that has the languages that you want. If you wanted a chinese language though, your going to need a MAIN that is something like CHINA_MAIN or TAIWAN_MAIN or something like that.