Hammersmith
Thanks to Lisa Wilkinson for this tip:
"The other day I went out foraging to Leg o' Mutton nature reserve by Hammersmith bridge. I found a cherry plum tree with lots of small red plums on it. It’s in the corner of the reserve closest to Hammersmith bridge and the river. I am cooking them tonight into a crumble. There are of course lots of elderberries, blackberries, nettles and hawthorns.
Also when you come out of the reserve back onto the path that runs by the river (approximately mid way from one end of the reserve to the other) there is a huge apple tree on the banks of the river. Although I found this tree to big to collect directly from the tree and most of the fruit below was rotting. The apples I did get were like granny smiths. "