You are on the right lines with one of those.
Watched the last couple of episodes of "The Girl Before"* before coming back to this puzzle.
*I should see if the book has a better ending
Been looking at the Cheddar Audax routes due to the proximity of the
Avon and lots of
Roman things.
Not sure about
shaded forest although a dip might be shaded; Mendip Forest maybe. Seems tenuous.
Coming down a
cliff could refer to descents around Cheddar.
Or there's Avon
cliff.
Not sure about the boat clue, which could refer to various bodies of water or a play on words.
Or I'm barking up the wrong tree.
Too late for me anyway. I'm off for some sleep!