The fuses in the plug tops will stop an overload on the cable. This is no different to tapping of a busbar chamber (industrial) in smaller tails and having a switch fuse inline after a meter or 2 of cable. Protection against over load does not always have to be at the source of the circuit.
So based on this assumption I could wire a single 13A socket on the end of some 1mm cable from a 50A MCB in the CU?