you might be interested in R.Hippisley Cox's book 'The Green Roads of England' - a wonderful study of old tracks - most of which led along watersheds - ie upland ridges between valleys. His maps of these roads do, interestingly, have a very different feel to a map which is about the coast.

Also of interst is that cover of the third edition (1927) has a drawing of the white horse on it. It's a lovely book with beautiful illusrations of many megalithic sites. Unfortunatley it's long out of pritn although i believe there are plans to make it freely available as an e-book