I've read all of these books and seen the movies and the Lewis Collins movie. Collins was/is a reserve SAS trooper as well as an actor.
I especially recommend Wilbur Smith's, "The Train From Katanga", later re-titled as, "Dark of the Sun." (Also the movie title although the movie has also been released as, "Africa Ablaze.")
Smith has also written other books featuring mercenaries, inc. the recent one I'm reading now, "Vicious Circle."
If you aren't familiar with his writing, go to his colorful site and read about him and his books. I've read him from the first, and he's still holding his own for the most part, although well into his 70's. Many of his books are set in Africa and have hunting themes. A good one long those lines is, "The Golden Fox."
He also has some historical novels that are not especially accurate, but which are stirring and entertaining.
The books sell very well on the world market, and he and third wife Mokhiniso (born in a former Soviet Republic) have homes in London, South Africa, Switzerland, and some other place that momentarily escapes my memory.
If you ever have the opportunity to see a selection of his foreign covers (anything but UK or South African), you're in for a treat. They are colorful and many.