Thinking about journeys by river in prehistory... The river Chew makes it way past Stanton Drew Circle, and winds on to meet the Avon at Keynsham which then meanders past Bath, continuing the circuit round; the Avon is joined at Midford by Midford Brook, and into Midford Brook a mile or so later Wellow Brook merges. Now Wellow Brook flows past Stoney Littleton longbarrow - so did the ammonite stone of SL get transported down the Avon, Midford and Wellow Brook from Keynsham where ammonites can be found?
I remember the river Marden at Calne, you could walk through the fields to a weir, or at least a concrete slide, children used to swim there till one day someone got drowned....