Tolkien spent in Oxford many years of his life, both as a student and as a Professor. Between the early 1930s and late 1949 he was also a member of the Inklings, an informal literary discussion group associated with the University of Oxford (many of the members were professors of the University). Is it possible that in their discussions they also talked about their books, receiving suggestions and support during the composition. 

Lyme Regis is a holiday place for the Tolkien family. Here Tolkien dedicated himself to the art of drawing and painting. A pencil sketch that dates back to 1928 shows a hill of Lyme (maybe the Tumble Hill) covered by tall trees. These trees are similar to the ones of two other sketches, that depicted places of Middle Earth: the island of Tol Sirion and the forest Taur-nu-Fuin.