Reverend

As for British underground comix, that's my specialty. I've been working on my own reference guide to that particular genre (shameless plug), but until that's ready, there's the aforementioned Comix: The Underground Revolution by Dez Skinn, but also Nasty Tales: Sex, Drugs, Rock 'N Roll & Violence in the British Underground by David Huxley, which can be found for cheap on Amazon: https://www.amazon.com/Nasty-Tales-Violence-Underground-Primal-Spinal/dp/190048613X. In addition to a lively history of comix in Britain, Huxley provides a list of publications, cobbled together from by Mal Burns' Comix Index: The Directory of Alternative British Graphic Magazines: 1966-1977 (http://www.ebay.com/itm/162172346588) and the Fast Fiction Info Sheets, many of which can be seen, in their entirety, on artist Ed Pinsent's website, which is another invaluable resource: http://comics.edpinsent.com/.

If you're interested in learning more about Spanish underground comix, Tebeosfera is an invaluable resource: http://www.tebeosfera.com/portada.php There's also the book, El Cómic Underground Espñol, 1970-1980, by Pablo Dopico, though it's now out of print and rather expensive on the secondary market, though affordable copies do turn up from time to time. https://www.amazon.com/Underground-Espanol-1970-1980-Spanish-Cuadernos/dp/8437622190

Canadian Comics Archive is also a fine site to learn more about Canadian undergrounds. It covers both old and new(er) publications. http://www.canadiancomicsarchive.ca/

Canuck Comics: A Guide to Comic Books Published in Canada is a good resource for Canadian undergrounds, though it's focus is not primarily on undergrounds themselves. You can usually buy a copy on Amazon for a fair price. https://www.amazon.com/Canuck-comics-MacMillan-Robert-Pomerleau/dp/0921101007

It doesn't seem odd at all that Kennedy missed Figments. A great many undocumented undergrounds from the '60s and '70s have surfaced since Kennedy published his guide in 1982.