as a white south african I should in current theory not have any say about whether south africa or any of the other few dozen former colonies chummy up to their former masters.

Wrong.   One of my grandfathers started life in a british concentration camp from which most of his family did not escape.   The british actually killed a higher proportion of prisoners than the germans murdered jews.  Fact.  Argue all you like, the facts do not change.

I am 50-odd and would assume that the european countries will find a similar level of lack of eagerness within former colonies to now embrace England, France, Germany, Portugal, Spain, etc

Just stay away