My house is built with the Gewiss switching products. (Gewiss.com)
The in wall box is a rectangular box of about 6cm height, 5 cm depth and the length depends on the number of gangs to insert. For up to three gangs the distance between the fixings screws is 8.5 cm which is almost as the US distance.
However the Gewiss design lets you combine switches and sockets in the same assembly.
It would be very appreciated if your firm could provide products to fit with this line