Thanks for the explanation.
I agree with Helli-Gurl's point re. distance and standards but at 15m you won't have a problem unless you wrap the cable around a fluorescent lamp or lift motor etc.
My revised suggestion would be ;
-purchase some good quality internal 'phone cable, about 20 m.
Not the flat type but twisted pair - Cat 5 will do nicely.
- run the phone cable from the current master socket in the
lounge to the PC
- remove master socket and install at the PC end
- install an extension or secondary socket in the lounge (you may
also need a junction box depending on the type of extension
socket used)
- use a spare pair in the 'phone cable to connect up the
extension socket back from the relocated master socket.
End result, you have extended the master socket to be close to the PC so no cable distance issues. The socket in the lounge has simply become an extension from the master socket.
I've done this in a similar setup, works fine, is simple to do, is reliable and cost effective.
If you currently use a separate microfilter, you may want to consider changing the master socket faceplate for one with a 'phone and RJ11 (inbuilt microfilter) sockets - about £11 as I recall.
The faceplates which use the Krone type connections are better. These are readily available from any decent Electrical Wholesaler vs. the screw connection types from DIY stores.