VARIOUS ENOCHIC APOCRYPHA seem to be alluded to in League of Extraordinary Gentlemen: Black Dossier:

JESS NEVINS' "BLACK DOSSIER" ANNOTATIONS
by Andy Khouri, Staff Writer [Comic Book Resources]
Posted: November 15, 2007 — More From This Author

The long awaited "League of Extraordinary Gentlemen: Black Dossier" is on sale now from Wildstorm, and that means Jess Nevins has been busy. Known in far corners of the Internet for his exhaustive annotations on some of American comics' greatest works, Nevins is a master who has been acknowledged by "League" creators Kevin O'Neil and Alan Moore, who've provided him with their own commentaries and remarks about his hugely impressive work.

Nevins has already completed his annotations for "Black Dossier," and CBR News is proud to re-publish his startlingly prodigious work here for our readers. To discuss Nevins' annotations and "Black Dossier" with fellow readers, don't forget to stop by CBR's Wildstorm forum.

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The Book of Enoch is not, I believe, a reference to the various books which are falsely-attributed to Enoch, the great-grandfather of Noah, but rather to the book in which Dr. John Dee and his assistant Edward Kelley took dictation of the angelical language from a set of angels.
Philp & Emily Graves write, "I think the reference to the Book of Enoch is possibly a double-allusion. Certainly the apocryphal Enoch talks of various Angelic beings (and is the reference for the Nephilim and Lilim, which are the offspring referenced on p26). Likely, therefore that Suttle (Dee) and Face (Kelley) communicate with the creatures from Apocryphal Enoch, and would then use such contact to write a LoEG version of Dee's Enoch."
Greg Strohecker writes,

I think Moore is referencing the actual book "1 Enoch" from the pseudepigrapha, as well as the writings of John Dee and Edward Kelly. In 1 Enoch, there is a section where it describes how some of the "Watchers", who were fallen angels, took human wives and had children with them. Their descendents were a race of giants called the Nephillim (not unlike the Titans of Greek Mythology). Here's the link and quote from Wikipedia: http://en.wikipedia.org/wiki/Book_of_enoch#The_Book_of_the_Watchers . "The first section of the book depicts the interaction of the fallen angels with mankind; Sêmîazâz compels the other 199 fallen angels to take human wives to have children." In the magical Enochian tradition “aethyrs” are various planes or worlds which surround and mingle with our own.

[...]

The mythos is nothing if not eclectic, with (to give a random smattering) references to Greek, Greco-Assyrian, and Egyptian mythology, Arthurian legends, and the Cthulu and Conan stories.