Take a look at the wiring and note how it appears to make your task easier later. If you can, taking a quick photo of the wiring layout with your phone will help. You should see one of two combinations of wiring depending on when the house was last wired: blue or black, which is neutral; and brown or red, which is live. Green and yellow represents the earth wire. Loosen and remove each of the screws holding each individual wire in place. If there is any obvious damage to the current wiring, cut off the damaged end of the wire and then strip back a little insulation to reveal the inner wire.