Are hinged covers necessary, bearing in mind that they will be under tables? The problem is that I can’t find with such sockets with USB. I’d have to have a third 1G for plugging a charger into.
If they need to be covered, would a box be a better idea? I could then use ‘ordinary’ 13A sockets. Unsightly (although under the tables) and quite a bit more expensive, plus big cutouts spanning the floorboards.
Another option would be flat plate sockets in a shallow recess, to make them flush with the floor.
Would back boxes be required? This is the ground floor, with only about 30 cm of space under the floorboards.