Any wiring after the master socket is the responsibility of the property owner. The owner should know where the master socket is located.
As I suspected, my landlord has said he doesn't know where the main socket is. Can you advise me how I can move forward on this? Can I still ask BT/OpenReach to come to sort out the wiring?
Yes, you can ask for an engineer to attend and sort it out but it will be chargeable. It may be cheaper to source a local telecom engineer.
Thanks for the quick reply.
In what is a really weird coincidence, I've just had to go up into the loft with a plumber to investigate a potential water leak (great house this!) and found the main socket up there at the end of a very long loose cable near my heating header tank. I've brought it down and connected my HH6 to it, and planned doing and posting all the test results here again. Would that be of help or should I just ask for an engineer to come?
Just did a speed test of the outside of the main socket, then another using the test socket inside, and these are the results. Doesn't look to be a material difference, with the test socket being marginally slower. Again these were done with broadbandspeedchecher.co.uk as bt.com won't accept my BT ID to initiate a test from there.
I would look at having the master removed from the loft and close to where your hub is. A long lead from master to hub will result in reduced speeds.
Just coming back to your "Your connection speed is nowhere near what you would expect from the dslchecker results" comment.
Having now found the master socket, and done speed tests on it, both from the external socket and internally using the test socket, and found them, to my mind, not that different from the the results I got initially from having the HH6 on secondary sockets what action do you think I should take to get an improvement?
It has been suggested that I re-site the master socket so there isn't so much distance between it and the HH6. Looking more at the cabling in the loft, I can see the black cable of the line entering the house goes to a GPO branded (!) junction box, and from this box there's a 10 metre cable to the main socket and other cables to the secondary sockets so the distance from main socket to HH6 is maybe 15 metres, being the 10 m to main socket plus 5m to secondary. Given that the speed test results aren't much different, I'm not sure I can justify re-wiring to the house owner.
Your advice would be much appreciated.
If that is where the external cable comes in you have what is known as star wiring which will kill broadband and is completely incorrect method of wiring.
that is just a junction box and where the incoming openreach line connects to the internal house cable which in turn goes to master socket you appear to also have another cable connected maybe running to extension which as @licquorice said creates star wiring you need to disconnect the extra cable then try hub stats again
Thanks to both of you for the quick replies.
It's like a furnace in my loft today so although I went up there for another quick look and to take the picture, I wouldn't want to go up there and spend time changing the wiring before re-testing! I reckon on that junction box there's input, output to main socket and at least three others all heading, I guess, to extensions. But is this something I should be doing myself as someone who knows nothing about how this wiring should be done or should I get BT/Openreach in to look at it? As it's a GPO box on the line to the main socket would it be counted as theirs, or does having cables from it to extensions make it the house owners responsibility?