Gotye - Somebody That I Used To Know

I bought a NME for the first time in months today (mostly because it had Blur on the front, and I got Blur tickets this morning). I saw the top 20 so thought I'd check it out. I was halfway through listening to this and thought "this sounds so familiar..." until near the end I realised it was weird accent singing it. My NZ friend posted this on her facebook months ago, and I liked it, but I kind of dismissed it because it's from Aus... Bad Hannah. Now I read it got number one in the UK?  Huh?