That large drop sounds like it could have been DLM intervention; smaller drops could have been an adjustment by DLM, or just a result of small increments of take-up.

How many changes happen without you touching a thing, and how many happen because you cause a power-cycle or reboot of the modem?

In reply to a post by kijoma:

As already mentioned, the more lines that go live via your cabinet the greater the crosstalk issue, this was the same for ADSL and is why people on long ADSL lines got slower and slower and some dropped off completely when more people closer to the exchange went live.

Although they have a solution for that in VDSL that isn't available to ADSL - vectoring.

At least they will when they've finished playing with trials, though iIt has gone live in Ireland.

So the have / have not and speed disparity issue from ADSL will still exist as will those who start with a working long line FTTC connection that then fails once take up escalates.

...

After all they can always put you back onto ADSL.

Don't forget that there would appear to be a third, middle, ground.

Openreach appear to be preparing for the option that lines still too long to get VDSL2 service from the cabinet could be offered the option of ADSL2+ from the cabinet.

aka GEA over ADSL2+, and seemingly targetted at cabinet distances of 2km+

The sync speed records are available on the Zen portal's "View Line Data" feature, whether the line is on Zen backhaul (line technology GEA FTTC) or BT Wholesale backhaul (line technology WBMC). This will show if there was a single drop in sync speed, or several smaller ones.

Ive just given up with talktalk fibre service, I was estimated 15 meg, I got 6 meg in april 2014, but now I get 4 meg down load and 0.3 meg upload on a good day.

I'm interested in the adsl service from the cabinet that WWWombat mentioned , does anyone have any more info on this ?

By the way my down grade has not gone well VDSL stopped 18:20 on the 4th sept 2015, but now not even a sniff of ADSL training, just a click on the line exactly every 4 seconds

ADSL2+ from cabinet - no sign of it as a product yet.

Believe it was seen as a USC type service, but Government seems to be more interested in alternatives for meeting the 2 Mbps target now.