Yeah, I'm US based and I run it on both 240v and 208v systems no problem - in either case, there's still only 3 wires (assuming you're using C13 or C19 plugs, which you probably are).  The Sonoff has the labels L (line), N (neutral) and E (earth) if I remember correctly - so it should be the same for your plug wiring, the only difference is that they call earth -> ground here typically.  Then just pay attention to their wiring diagram:

https://www.itead.cc/wiki/images/c/c7/Sonoff_Pow_Wiring.jpg

But as you see, they're tolerant 90v to 240v, so they work great.