The Ro-Ro skip is 20 cubic yards capacity, they come bigger, but for inert material (soils/bricks etc) anything bigger then the hookloader would never pick it up, never mind the the collection vehicle would seriously exceed its legal gross weight! (Think they can carry around the 16tonne mark legally, on 4 axles.)
Any container placed on the public highway needs a road permit from the local authority, I have seen Ro-Ro containers on the road round here, but may well be up to the discretion of the individual authority as to what they will allow.
Nice pics Eddy, thanks for sharing.