Hello Wyrd,
I don't know if your research covers sacred springs and wells in London, there are quite a number I think. I don't believe TMA extends to these but we have a growing database of locations and photos here, and you'd be very welcome to contribute. http://www.megalithic.co.uk/asb_mapsquare.php?op=map&sq=TQ&sitetype=45
Cheers,
Andy