Hi, i have a US 1.1.1 iphone that i have unlocked with anysim 1.1

I hear that current UK phones dont need unlocking as any O2 sim will work.

Since i'm on o2 anyway - i was wondering if used onesim, then did an upgrade to 1.1.2 would my sim work ?

or is there something unique to the uk phones ? ie bootloader or something that would stop this from working ?