I've also learned from another thread, that it is not safe to make assumptions around Broadband installations, so does this look like the master socket? It is sited in the garage, and is easily the nearest phone socket to where the Telecom box is sited on the outside wall. I note though, that the cables are looped down from the loft space, and back up again, which does seem completely right to me, unless the cable from the outside Telecom goes up the cavity to the loft and back down to this socket.

Can I usefully pre-empt the VDSL install by running Cat6 cable from this socket to the socket behind my computers, And should I offset the run to avoid the power cables in the power socket above the telephone socket? I'd do this on top of the Gib Board rather than try to pull it through the cavity.
Can you guys identify the existing cable from the image? It shows the initial installation as November 1999.
I've also found the modem stats on the HG360b. Using the divide by 13.1 formula. it puts me at 900m from the cabinet. If the cable came down my street, and straight off to the phone point, it would be 450m, so either the reading is wrong, or the cable takes a more roundabout route. My speed has remained at 7.4/.8 from day one.
Line standard ADSL2+ Channel type Interleaved Downstream line rate (kbit/s) 16319 Upstream line rate (kbit/s) 972 Downstream SNR (dB) 12.6 Upstream SNR (dB) 12.5 Downstream line attenuation (dB) 13.5 Upstream line attenuation (dB) 6.3 Downstream output power (dBmV) 18.9 Upstream output power (dBmV) 12.1 Downstream CRC 0 Upstream CRC 4 Downstream FEC 146 Upstream FEC 3014
I appreciate the help you've all given so far. Many thanks