This family tree is based on my own research as well as other source material that can be found on the internet, or in books. Despite this, there are some inaccuracies as there is sometimes conflicting information.
It is based on first degree initiations, although in some cases a different person may have given a second or third degree initiation. Some of these are indicated by intermediate yellow boxes.
The tree is not complete and does not include everyone that could be on it.
The years given indicate the first initiation, and in some cases are only approximate but should be within a year either way.
Dancing with Witches by Lois Bourne
Fifty Years of Wicca by Fred Lamond
Rebirth of Witchcraft by Doreen Valiente
Craft History Chronology by Roger Dearnaley
http://www.bcholmes.org/wicca/gardner.html A website with some background history.
Archived version of aWebsite about the various lineages focusing mainly on the USA and Canada. There are far more traditions to be found in North America, something that has almost certainly been a result of a much greater population than the U.K.
Notes on Gardnerian Witchcraft in England by Fred Lamond.