I live in Wandsworth (in south-west London) and cover two patches:
(1) London Wetland Centre (Barnes WWT) plus the nearby Barnes Common and Beverley Brook.
(2) Wandsworth Common and the Thames between Battersea Bridge and Putney Bridge.
I started birding in 1980 when I lived in SE Essex and Lesser spotted Woodpecker was a garden bird (from the nearby Belfairs Woods). My local patches were Two Tree Island and Hadleigh & Leigh Marshes which turned up a few good birds (eg Cream coloured Courser found by Colin Todd and Ring billed Gull).
I didn't do any birding in the UK for almost all of the 90s but a series of overseas trips got me back into it and have now been back birding again for nearly a decade. Birding gets squeezed between work and kids but I usually get out a couple of times a week, if only when taking the kids out for a walk.
I have an erratically updated blog at South West London Birding