”I'd start with a filtered faceplate. Using solid core cable (CW1308 or Cat5/Cat5e/Cat6/etc.) use a pair for voice and a pair for data and connect using the IDC terminals, not the sockets. At the other end connect a double network faceplate, or if you want to get exotic dedicated RJ11 and BT phone sockets.”
I used 2 pairs of a solid core CAT5 and connected to the internal terminals 2,3,4 and 5 of the main BT socket, connecting directly with the incoming pair (A and B / terminals 2 and 5). The main socket is an old one, so probably not filtered though I am using a plug in filter for connecting the router. The other end was a standard secondary phone socket. Prior to that though I ran it into a junction box, so maybe I will try it directly into the socket outlet to see if it was bad connections. Thanks for the info, I will look into the suggestions you made and see if I can resolve it knowing the cable should not be the problem, I like a challenge.