Getting back to holy wells; one of the best ways to find wells/ancient sites is to to read around the early celtic saints/desert monks. Over the weekend was tracing St.Trillo's skull and well and found a book by Elizabeth Rees (nun) Celtic Saints in their Landscape, she mentions several wells and prehistoric stones that are found in churchyards - "The stone in the icy corner"(its in the porch) in Corwen sounds appealing, she has also written "Celtic Sites and their saints". Another book, is Terry Breverton - "The book of Welsh Saints".
These early wandering monks would have sermonised from the old pagan stones, and probably sheltered as well..