In a country half as densely populated as the UK- especially its South-East corner- it is obviously easier to build straight high speed rail lines or such huge statements as the Millau viaduct in France. However there is also a far greater will to do so. In Britain we spend billions on invalidity benefit and call it "investing in people"; in France they genuinely do "invest" in infrastructure. It is an investment that allows the French to travel across the country in 2-3 hours. To live in Mid France and still work in Paris: the equivalent of living in Sheffield and working in London, with only a one hour travelling time between the two. By contrast, it takes hours to simply cross London. There are no high speed RER trains in London, which make travelling in Paris so much faster. Cross Rail, which would be RER 40 years later, remains a distant dream, while in Paris there are already 7 or 8 RER lines.
The British economy is choking under the weight of the need to concentrate so much in London and South East England because it takes to long or is too expensive to travel if one is based outside that region. Paris and the Ile-de-France have far fewer problems because of the vision and the ambition that they showed in fixing up their infrastructure. Sure, not all of it works: the Mitterand Library is a poorly built, ugly shambles. Yet still one can not fault the idea. The Nimby-ism and catastrophically expensive real estate market in the UK are impoverishing the whole country.
And there is no-one to even start the national debate about what we must do.