you say the cable is not long enough, what cable?
is it from an existing socket you are moving are you spuring from another socket?
the answer is yes you can, but i would be inclined to change the whole cable run, because to join a 2.5mm cable (as you should be using for sockets) you must use a 30 amp junction box that you can not bury in the wall, so it would be (as i mentioned) better to change the whole cable
Can you not use terminal connector joining the wires together inside the existing socket box and use a cover plate ? I've got that in one of my room. Is that okay ?
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