Gets difficult with current regulations, unprotected wires can only be run vertically and horizontally from outlets. If you conceal what was an outlet there will be no indication that the wires exist. Leave the sockets or fit maintenance free junction boxes and a cover plate over the holes.
To comply with regs it will be necessary to either fit blank plates over holes to show wiring is there or to remove or isolate the cables further back on the circuit by possibly locating drops and cutting and joining correctly to maintain the circuit.
If you simply put connectors in place of outlet and cover over no one will know that wires are running up/down walls.
Sorry won't be easy but has to be done.
I'm pleased you asked though!
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