Please note that it is now a technical requirement that all sockets in a house are protected by a 30mA RCD. Many older installations do not have this. While there is no obligation on the householder to upgrade your entire installation, any new socket additions would need to include
RCD protection. We can advise of the various ways of achieving this.
In most cases is it also necessary to RCD protect new wiring to sockets and lights etc that is concealed in walls. This provides protection against electric shock when nailing or screwing into the wall.
See also How many sockets do I need?