We had a similar problem on a 51 plate Clio, turned out that the body control unit was playing up intermittently. Would be worth carefully checking wires from both window switches back to control unit and monitoring these when you lock and unlock as well as operating the switches. We ended up modifying the BCU by cutting the circuit on the BCU's PCB to the window relay and connecting the switch direct to the relay, thus bypassing the BCU's control of the relay. Worked ok but obviously looses one touch operation.