What developments did eventually push British political elite towards the ECSC?

The ECSC financed and built more than 150 000 council houses between 1952 and 1979 throughout the whole Community. The High Authority also made great efforts to conclude a European Convention on Social Security for migrant workers, as well as working towards the introduction of the five-day week.

That may be (partly) the political and economic significance of the ECSC.