Usually there is a box on the outside of the house where the cable - for example - comes out of the ground. There is then usually a cable from that box in through the wall to the master socket. If you can find the outside box, I'd be inclined to remove the wiring your side of that box. That leaves the service intact for other future users.
This is not legal advice though, just practical.
I haven't touched what is in the box outside or anywhere near. Literally all I have done is clipped the wires closest to the facia inside house