It should go line - master - extensions
The idea is the test socket bypasses your extensions. Does it?
If so - easy fix.

I believe for simplicity the engineers MAY HAVE done the following:
Line - all extensions (with one of the extensions a master socket).
So the extensions are not going via the master.
If this is the case, it would explain your slowdowns / be a pain to fix.

Ok, so I've managed to get inside the sockets in my house and find out the following:

I started by taking the faceplate off the master socket in the bedroom and plugged the HH5 into the test socket..... I was immediately presented by 32mb DL and 5.8mb UL - a lot better than what I was getting before (22mb DL, 3mb UL) when the faceplate was plugged in. When I plug the faceplate back in, I immediately get the slower speeds. Perhaps you may know what is causing the problem from my photos and description below. They are labelled up accordingly:

Phone sockets in house

You will see the first socket in the loft (a couple of photos, and I was very careful!), this is where the BT engineer 'bypassed' this socket and connected the outside BT line to my internal wiring which then goes down to the master socket in the bedroom.

Then the master socket in the bedroom is where the HH5 is connected. When I take the faceplate off, the extension socket (where the telephone is connected to) is suddenly disconnected (so far so good) and my speeds jump up, as mentioned above. You can see the faceplate has the downstairs extension. When the faceplate goes back in, slow speeds come back.

Lastly there are the photos of the downstairs connection where the telephone socket is. I did mention before that there was another extension socket - this has been completely disconnected, i.e. nothing connected at either end so can disregard this.

Interestingly (and this is the first time I have actually noticed) when listening to a dial tone on the telephone, the amount of interference I can hear from the line, i.e. if there is anyone walking through the house or if I knock on the wall, I can hear noises on the line.

Hopefully with the above description and photos, someone may know whats going on.

Thanks,

If good at the test socket, then fitting a VDSL faceplate such as this one at £9 + p&p on amazon should isolate the effects of the extension wiring from the VDSL signal.

No wiring changes needed the faceplate just slips in-between the existing small faceplate and the back part, pictures at http://www.coolwebhome.co.uk/faceplate/ should make things clearer.

It sounds like a classic case of noise being introduced due to all that extension wiring and a filter will pretty well sort that out. What would also be interesting is the stats from the modem (which, if you have an HH5 you can get to be going to the admin page, go to troubleshooting and log onto the admin account to get to the helpdesk page). Of particular interest are the attenuation (up/down), the noise margin and the maximum and actual data connection speeds. If you had a lot of noise on the line due to the extensions you may have interleaving turned on (which will cost speed) and a few other things. Also, due to the way the line has been profiled in might take a little while before everything is optimised properly.

That said, the upstream rate is rather low and I wouldn't be surprise if your cabinet isn't something like 800m away. The attenuation figures will give a clue.

As Mr. Saffron says, the first thing is to get one of those filters.

Thanks for the advice. Ordered a VDSL faceplate as recommended. Will update with results when delivered and fitted.

Here are the line stats: (line is surprisingly sync'd this evening at a slightly faster than usual rate with faceplate plugged in).

Also, distance to cabinet is approx 480 metres.

1. Product name: BT Home Hub
2. Serial number:
3. Firmware version: Software version 4.7.5.1.83.8.204.1.11 (Type A) Last updated 04/09/15
4. Board version: BT Hub 5A
5. DSL uptime: 0 days, 02:06:57
6. Data rate: 3958 / 28475
7. Maximum data rate: 4224 / 33083
8. Noise margin: 6.3 / 6.0
9. Line attenuation: 33.2 / 22.1
10. Signal attenuation: 31.9 / 19.6

If you compare these stats with mine, then you clearly have a slightly longer line (or at least one with a bit more attenuation), but it's less that 1dB downstream and 2dB up. I think you've got potential there for closer to 40mbps sync speed with a faceplate. One thing I do notice is a fairly big difference (downstream) between the maximum data rate and the the actual. That's often a symptom of interleaving being on, perhaps because of lots of errors on the line. You may find after a while with a filter installed that this might disappear. As it is, I'm getting more than twice your downstream rate with less than 1dB attenuation.

6. Data rate: 9753 / 58594
7. Maximum data rate: 9902 / 58106
8. Noise margin: 6.4 / 5.8
9. Line attenuation: 30.5 / 21.5
10. Signal attenuation: 30.3 / 20.3

Just wanted to let you know, the VDSL faceplate came in, fitted to original master socket and now getting speeds of around 34mb DL, and 6mb UL so much better than before and i'm very pleased.

Thanks for MrSaffron and others for all advice and help, very much appreciated. Posted the same problem on the BT forums.... still waiting for a reply so I know where to come to next time!

Have another slight issue about 5ghz and 2.4ghz wireless but will open up a new thread about this.

Thanks again and have a nice day

That's good to hear .

By "original master socket", do you mean the bedroom one, or have you somehow reverted to the loft one?

Sorry, I should have confirmed. I left the socket in the loft as behind the panel was merely just the external line wired into the existing house wiring (as per my original photos) which then goes into the master socket in the bedroom so I put the VDSL faceplate onto that.

Would it be worth having the external wire that goes straight into the loft, moved to go to a better position in the house (i.e. The hallway) for optimum performance? Or leave things as they are for now?

Probably very little difference, and possibly costing well over £100 if done officially.