im pretty sure ive seen some of those temporary urinals up in Brixton? on electric avenue, beside Iceland if im not mistaken.
These should be standard and plentiful anywhere with a late night economy, or basically anywhere people go out to get pissed. They cant cost much to put there and save all the bad feeling and sanitary problems with people pissing wherever they see fit.
ill be honest, Ive been caught short before and had to go somewhere other than a toilet, because there are almost always never one available. always picked very discreet spots and nowhere like a persons front door. if the urinals were provided they would get used and solve these problems, its not rocket science.