The supposed shift in "living standards" is actually an artifact of the dollar’s depreciation. The article admits this, which just makes it even stupider.
[T]he right way to do this sort of thing is to strip out the effect of exchange rates by converting pounds to dollars using purchasing power parity (PPP). Wikipedia has a nice chart which shows that, according to IMF data, in 2006 the UK’s GDP per capita was about 22% lower than ours and that number hasn’t changed much since then.
By most of these measurements, by the way, Germany’s slightly poorer than Great Britain. The United Nations Human Development Index is an alternative way to measure national well-being that’s broader than GDP-based indices. The US (#12) also beats the UK (#16) there, and both countries beat Germany (#22). However, the HDI differences between these nations are miniscule, and everyone loses to Scandinavia and France.