In many ways the current government surpasses Thatcher in its support for neoliberalism, so there's no doubt it'd be considered right-wing in any country, and since the Tories have largely been aping the Republicans for the past thirty years, I don't really get how they'd go unconsidered (but OMG they support gay marriage, so that must make them centrist!).
That might be part of it; from a North American perspective the British tories are rather socially liberal... when compared to the CDN Tories, AUS Liberals or in particular the Republicans... many are bible breathing radicals who to this day are very socially conservative. While we would see centrists as those who are Free market neoliberals but balanced with that liking gays and immigrants side and see, they also don't see the government as the devil (like CDN Liberals or Democrats)
What would really be interesting to compare would be the decline of the moderate, centrist parites... look at the CDN Liberals, LD's in the UK, FDP in Germany, MD in France... the world seems to be less willing to support middle-of-the-roaders now a days.
