I have read a few books about this subject, however, the most compelling so far is: "The Holy
Kingdom: Quest for the Real King Arthur: by Adrian Geoffrey Gilbert, Alan Wilson, Baram Blackett".
Unlike some other books which had long complicated explanations of how place names had been altered and why - going into the breakdown of languages and words in circuitous paths throughout jumbles of events and invasions and theories - the names of the related places discovered in Wales and described in this book have the same names as they did back at the time when Arthur is thought to have lived, and are the same names that were mentioned in the stories and legends, so there was no need for big explanations for names of towns that seem to have no connection to anything that has come down to us from the time of Arthur.
As well, on the land discovered to have been close to his general home area - the battle mounds still exist, which was not the case in the writings about other areas - prompting again the need for theories and explanations to support the proposed connections.
In a rather sad twist on modern development - the authors were only one step ahead of bulldozers preceding construction of a new townhouse subdivision which was about to remove all of the traces linking the area to Arthur and had to work feverishly to dredge up the funds to purchase the area before it was bulldozed into oblivion.
However, happily, they were that one step ahead although from the book it would seem that no-one really cares much about preserving that place - other than the authors. Hopefully that changed with the publication of "The Holy Kingdom".
This book is a "must read" for anyone who realizes (either through intuition or research) that there are reality-based reasons for the legends and myths that have come down to us.
The dedication, commitment and hard work that went into the research and writing of this book make it a worthwhile investment in time and energy.
Through everything I've read about Arthur - it seems that most of the claims for his connection to different areas was based on the marketing motivation. Once monks discovered how lucrative travellers could be to the financial well-being of their "local" attractions and to their churches and monasteries - there developed a competition for the tourist trade. This spawned great motivation to find all sorts of creative ways to connect to the legend of Arthur - the relics and headstones in their vicinity.
In the location uncovered in "the Holy Kingdom" there was no such fabrication - the land is as it was, perhaps even preserved deliberately by being kept peaceful and hidden - preserving the peace and natural purity of the location.
All the best to you in your investigations.