I wanted a British phone box to go with a Tardis I printed years ago, so I found this SketchUp model on the 3d warehouse, did some proportional corrections to match a K6 photo, modified and scaled it for 3d printing.
All components were printed with .2 mm layers and .4 nozzle. Use variable layer height on the top of the roof to reduce the stair step effect.
The main frame and the actual phone require supports, the remaining parts do not.
Print 3 doors, and 1 of everything else.
The wall directory and phone have to be glued to the back wall. The doors and roof friction fit into recesses in the main frame.
There is a pdf with the “telephone” sign and wall directory that can be printed, cut-out and attached in the recesses with glue stick.
The author remixed this model.
I modified this model for 3d printing by separating the various components, simplifying some details, and eliminating some overhangs to reduce supports. I also did some stretching/shrinking of various design elements to better match the proportions of a K6 phone box.