Another dennis wheatley fan here. Like kitty_kitty i've only read his black magic books.....actually, come to think of it i did read one of his ww2 occult novels, but yes, i loved 'devil rides out', gateway to hell', ' the satanist' ,To the devil a daughter'.
Think the op may be a bit young to remember this, but i did subscribe to the heron red 'leather' edition books from a sunday paper advertisment back in the seventies . Didn't get them all though as i only went for a select few. I sold them a years back, but managed to find a them again on abebooks. So i bought Devil rides out and strange conflict. Great to see them again. So many memories .
Think you'll find his books out of print as there not very PC for many people in this day and age which is a shame.
There was, and i think still is, an excellent site dedicated to wheatley:
http://www.denniswheatley.info/contents.htm
Sadly the original owner passed away recently but the reins have been taken up by one of the sites members.