Well, its actually a quite common mistake. Mix that with a borderline alcoholic phase and insomnia, I don't think it's even a stretch to accidentally mistake the two.
How about the fact that it has been mentioned several times in this thread that its an Australian show? I mean, confusing Australians and New Zealanders would be OK. For a non-Australian it might be hard to tell the difference. But confusing England and Australia is like confusing the USA and Mexico.