Currently re-working my way through Fleming (again), having originally devoured them all as a teenager back in the 80's. Am about to start on FRWL - my absolute favourite Fleming Bond novel.
I have read all of Gardner's continuation novels - IMHO the quality dropped off towards the end of Gardner's run, but the first three - Licence Renewed, For Special Services and Icebreaker - are terrific entertainment.
Haven't read Colonel Sun in a long time either, but I do remember it as a hard-edged, rather brutal thriller, and far superior to Sebastian Faulks's rather poor Devil May Care.
I read Benson's Zero Minus Ten when it first came out, and found it passable, but haven't bothered with any of his other Bond stuff. Likewise with Charlie Higson - SilverFin = good, the rest = a bit meh.
I also remember reading Christopher Woods's adaptations of TSWLM and MR in the late 80's, and finding them - to my surprise - to be pretty close to Fleming in tone and style.
‘I've got a little itch, down there. Would you mind?’