Any lamp in your home, office, or shop that is turned on and off from a single location is controlled by a one-way switch. These switches are by far the most commonly used switch in the home.
To replace that switch is not a big task, just should followed carefully.
First switch off the mains supply at the consumer unit and remove the fuse for the circuit you are working on. Undo the two fixing screws on the switch and pull out the switch from the mounting box.
The existing light switch should have two terminals only, if it has three – one at the top and two at the bottom then it is a two way switch. If the third terminal is not connected then it can simply be replaced with a one way switch.
Unscrew the terminals and remove the conductors from the original switch. Replace the conductors in the new switch in the same positions as the old switch. Ensure the terminals are tight. If the new switch is metal e.g. brass or chrome, then it should have an earth terminal on the metal case. This should be connected with a short length of earth wire to the earth on the mounting box inside the switch.
Replace the new switch in the mounting box and secure with it the two screws.
Power can now be restored at the consumer unit.