Me and my gigging mate gave up on trying to park anywhere in London, far too much hassle and time involved, and that was before congestion zones. We’ve used JustPark for a few years now, coming in on the M4, but most of the ones we used to use are no longer operating.
The most recent trip my mate found one at a sailing club behind a filling station on the Great West Way, which did involve driving right to Hammersmith, turning under the overpass and driving back, and the space is behind the filling station just before the roundabout. It’s confusing, you actually have to turn off and drive through the forecourt then left down a little road to pretty much a dead-end by some gates overlooking the river.
The address is 60 Upper Mall, Hammersmith, W6 9TD.
It’s a bit of a hike back along to Hammersmith, and again at night going home, but it has the advantage of just driving straight out onto Great West Way then onto the roundabout.