An interesting thread indeed! You may find this year 1815 map of interest. As suggested by Derek the pond at Spring Grove/Style Hall Farm flowed eastwards towards Sutton and Elmwood Road. There was also a pond on Turnham Green called the Packhorse Pond. The higher ground around Harvard Road would have seen water finding its way down to Wolseley Gardens and Whitehall Gardens. I wonder if Mr Shepherds "Jersey Nurseries" at the end of Whitehall Gardens was well hydrated for his market garden.