Extending cable on 'Virgin' phone socket

[mirage1]

Hope someone will be able to help.
I had BT as my main phone (downstairs) and had VM installed some years ago with a secondary phone line for office use.The main VM socket was brought in onto the landing upstairs (up the outside wall). The cables from these sockets were routed into a bedroom which we used as an office. I have now moved from BT to Virgin and so the main socket is upstairs in the redundant office/now bedroom. This socket is quite far away from where we usually use the phones (downstairs in the lounge and kitchen).
So, I bought a three piece set of wireless 'Panasonic KX-TG 3281' to get around my problem....it didn't!
As the main phone has to be plugged into the main socket, in the upstairs bedroom, which is a long way away from the downstairs rooms, the reception is terrible, so I have to sit in the hall to get good reception!!
I have looked at the socket that come in from the outside onto the landing and need to extend from this to downstairs. Does anyone know how I do this pleeease - see photo.
It looks really scary to me but can't afford the prices that VM are quoting.
Finally, can I get an electric shock from any of the cables if I do dare to try do it myself. You can tell I'm blonde can't you???!!!