Summary

In the UK sockets and light switches use standard electrical boxes, either sunk into the wall, or surface mounted. The surface mount box (single, or double width) can make useful project boxes, especially for home automation applications. Displaying temperatures, mounting switches, etc. (see photo of example with TFT display)

Blank face plates are available but in some applications a 3D printed 'custom' cover may be better. This OpenSCAD model generates a plain face plate (single, or double) but may be modified to add apertures for displays, holes for switches, etc.as you require. A starting point, at least.

See here for video https://youtu.be/pbVAiODsPJE