Australia lost to Zimbabwe in a world cup league game after winning the 2007 world cup. India got smashed by BL after being world cup runners up in 2003. So many such instances. That's why called an upset.
I dont regard Eng as the best test team or something. They need to improve a hell lot away from home (in fact all teams travel poorly these days). But they aren't as bad at home as you make them out to be.