A source from 1990 saying such signs existed in 1970 is not much evidence that they are "common" today.

None of those references document the existence of such signs in the last generation. Local or national government bodies and quangos make a habit of responding to issues like specific forms of discrimination long after they've ceased to be something they actually have to put an effort into dealing with. You can always claim success in making a problem disappear if it already disappeared before you came on the scene. (That Bristol document is an honest attempt at doing something positive, but officialdom is just as prone to repeating urban legends as the general public).