Thanks to Alan Belson for the following:
Here are some pics of Legrand's 'Mosaic' receptacles being fitted, [to first fix] in our remodel. These are an interesting departure from the traditional 'pull it all out of the wall by the guts' design, and while a bit complicated they work very well indeed, being firm and solid with lots of themed options. The design is modular, with a choice of gangs and module outlets. Still made of thermoplastic and not bakelite, but a great improvement. There are other options in the catalog- too many to post here.
Description below each photo.
Pic 1. Drill 65mm holes for plastic drywall box with holesaw. The boxes have 'pilot holes' for accurate marking of drill positions.
Pic 2. Fit box. The duplex and triplex ports need slight trimming with a Kraft knife to link the diameters. Fix is by 'tongues' screwed up behind the drywall, which in this case is 13mm/1/2" thick. Tongues 'auto-locate' with a clever cam mechanism, which works fine.
Pic 3. Fit Plate. Duplex shown, this is heavy-gage galvanised and passivated steel. The screws are already in the boxes and fit into keyhole-slots for easy assembly and levelling / squaring up.
Pic 4. Fish cable through box. It's necessary to break out tabs in the box rear to suit cable or 16mm plastic sheathing [ gaine ]. Here, the other side has not been plasterboarded yet, making wiring easier.
Pic 5. Showing modules snap-fitted after wiring live/hot neutral and earth/ground. No polarity is shown in the module, but I always wire up with live on the left, earth at top for consistency, see later pics. The module snap-fit is strong and impossible to remove without tools. Note my mistake- drilled too near a stud, but easy to plaster a saw-waste disc back in with some spackle!