That's the first time I've thought of myself in the mid-Sahara

An apt comparison however with people still on sub-4Mbs ADSL2+ .

PMSG, your line is below the handback threshold. So it looks as if there may be a fault. Phone Pn and let them do some tests. You can do this online but i'd suggest doing this the phone.

First of all thank you to everyone who contributed to this thread.

There has been a most unexpected development which I would like to share with you. I took the advice to complain to PlusNet about my BB speed. The agent said he thought he could see what it was and he would request Openreach to change something. Thus took a few days and then my speed improved from about 14.5 to 15.5 which was just about in line with the guaranteed minimum speed. I was not too impressed with this but was even less impressed with the price the offered me when I said I was going to leave them. So I switched to Vodafone (I have always previously had fibre from PlusNet or BT in the belief that as BT controlled the infrastructure they would get the best performance). Anyway with some trepidation and solely to save money I switched. I am now about three weeks in and I am delighted to say my Broadband speed is over 24 mbs. I am absolutely delighted but also flabbergasted that my new supplier can give me so much better performance using the same (presumably still impacted) Openreach FTTC infrastructure.

Has anyone else had an experience like this? Can anyone explain how Vodafone make the FTTC go faster for me?

Different modem, e.g. may have been one of the older Home Hubs that did not play so well with some lines.

Maybe the DLM has reset and currently happy, but it is possible in time that errors may arise and speeds drop over time

NOTE: It is Openreach who control the VDSL2 hardware. Nothing to do with with the BT Consumer division.

A better VDSL modem in their router perhaps ?