Gentlemen

Yes I did think of the "Wild Geese" when watching the Patrice Lumumba movie as the "ex-President" character in the movie is obviously based on him. Plus the location of the operation which is obviously the Congo under a different name. Michael Hoare the originator of the true "Wild Geese" also was infamous in that conflict.

"The Mercenaries" or the "Dark of the Sun" I had forgotten. Will need to try to chase it up.

Another which is not Congo based but more West African based is "The Dogs of War". A excellent movie based on a even better book by Frederick Forsythe. I like the soundtrack at the end of the movie.

A new movie of course is "Tears of the Sun". Again West African based and official troops but in the too common African civil war setting.

A fictional book never made into a movie is "A coffin full of dreams". This is no longer in print but I managed to get two copies of it. Ordered one from one location and it took so long to come, that I had sourced and ordered another from another seller.

More suggestions if they exist please.