When working around any electrical power socket or light switch the safest thing to do is to isolate the power supply at the Consumer Unit (main fuse board). The power sockets and the light switches in a house are on different electrical circuits therefore you will need to isolate all the relevant fuses so that you can carry out the work safely. It is always a good idea to attach a warning label on each isolated (off) fuse in the consumer unit to warn other people that it has been deliberately isolated (turned off) and that they should not turn it on.
Consumer Unit often have their fuses labelled giving individual circuit details e.g. Ground Floor Sockets: 1st floor Lights: Kitchen Sockets etc. Do no assume these labels are correct as sometimes they are wrong. Isolate the fuse with the details for the circuit you require by moving it to the OFF position and then test the circuit as detailed below.
I find testing with an appliance the easiest way to identify the correct fuse in the Consumer Unit for when it goes off you know the circuit is isolated. Plug in and turn on a radio or a Hoover in the room where you are working and then systematically flick each fuse to the OFF position until the appliance goes silent. Do double check that the socket is isolated by trying to turn on the appliance once more, it is safer to check and to be certain it is off.
Also systematically check all the power points in the working area individually to confirm they are all isolated (OFF). It is important you that check each individual power point as it is possible than a power point in a room may be feed by a different circuit to the others. To quickly check that all the sockets are isolated (OFF), again plug in an electrical appliance and test to see if it will power up.
Remember to return all unrelated fuses to their original positions and attach a warning label over the isolated (off) fuse to warn other people that the fuse has been turn off deliberately and they should not turn it ON.
Remember electricity can kill so do not take any unnecessary risks, if you are uncertain about what you are doing, then do not proceed and seek help from someone