Do Facebookers never venture outside of cities? Because maybe the UK is weird, but getting 2G even in developed areas isn't that uncommon for me. Sure there's 4G in cities and 3G in many places, but there's plenty of places with poor signal or outdated transmitters (like the town I live in). (This is especially noticeable if you're in a train or a bus where you're frequently changing cells.)
Unless I was in a city, I only had 2G signal, and in a few places I didn't even have that (but those were rare).
Edit: for reference, my carrier at the time was Simple Mobile, an MVNO of T-Mobile (I'm no longer with them anymore: I just activated Project Fi today).