Minimal number of Constellations (and Stratocruisers) was all about supporting British types and British manufacturing industry.
No it wasn't. As WHBM indicates Britain was bankrupt at the end of the War and did not want to spend valuable rare dollars if there was a home-grown "alternative". Hence the Canadian-built Argonaut with Rolls-Royce engines - very little US dollar content. BOAC would have loved more Connies - but there were no dollars available to buy them with.
Each time BOAC bought American aircraft (first the Constellation, then the Startocruiser and finally the DC-7C) they had to provide proof to the UK Government that they were being severely disadvantaged in competition with US and European airlines.