Try these:

http://www.rocksandpebbles.co.uk/Playscheme.html

We used the Myatt Gardens scheme when it was run by Lewisham, and were very happy with it, but now my boys are older they go here:

http://www.lewishamcommunitysports.com/

You don't have to be sporty to enjoy it - mine are woefully non-sporty and love it at the St. Dunstan's venue, but not the Prendergast one (the Stillness location was only temporary while there was building work at Prendergast).