I recently worked in White City (west London), a number of the BT phone "boxes" are free to use (and have free WiFi and USB charging). BT are happy to offer all of the free extras in return for being allowed to have large LED advertising screens on the "pods".
A few years ago there was a resurgence in public pay phones (not owned by BT), again because of the opportunity to have LED advertising screens on high streets. Many of the ATMs also have LED advertising screens on the reverse side.