Keen to see the outcome of this - will inform my decision on which to read first. And which to avoid! Do they work as well having not read an awful lot of Fleming, or would you recommend getting clued up with the original stories first?
Optimally, you should read Ian Fleming first as his novels are well worth reading. However, off the top of my head, the only book that must be read before Raymond Benson's books is On Her Majesty's Secret Service. That is a critical intro to Never Dream Of Dying.
However, when reading Benson, you should make sure to read High Time to Kill, Doubleshot, and Never Dream Of Dying in that order as they are a very connected trilogy. The other three Benson novels are not as critical to read in order although The Man With The Red Tattoo clearly takes place after NDOD.
And regarding Fleming's OHMSS, that also forms the middle part of what is often called "The SPECTRE Trilogy", which features Thunderball, OHMSS, and You Only Live Twice. The Man With The Golden Gun also clearly comes after YOLT and should be read after that novel as well.
And for what it's worth, John Gardner's trilogy (also dealing with SPECTRE) is For Special Services, Role Of Honor, and Nobody Lives Forever which should be read in order.