I use the one at Sainsbury’s in Lower Sydenham for the car while the missus is doing the shopping - I’m based in Bromley South . It’s £1 for 3 mins and you choose the setting, i.e. water only, shampoo only, etc. Here’s the address
Southend Lane
LONDON
SE26 4PU
There’s another one at the Total garage on the corner of Croydon Road and Whitmore Road in Beckenham but I don’t know if their machine is similar to the one at Sainsbury’s.