(Unplug your phone line.)
Having upgraded to fibre on 14th October, all seemed fairly well, with speed that gradually increased, until it reached 30Mbps on the 18th, briefly.
For a while, it averaged about 20Mbps (we were promised 39-40Mbps), and then on November 9th it plunged to 1Mbps.
We reported it to TalkTalk and an engineer came out. While he was here on the 12th, the rate was poor, but he tried his 633 and it perked up a little, back to something fairly acceptable. Oddly, the improvement stayed on switching back to our 633. He booked a BT visit for the next Monday or Tuesday, as he said he had seen a line fault.
On Sunday at 6pm, I was called to be told that the BT visits had been cancelled, as there was no line fault. I was asked to do traceroutes, pings and supportal speed tests, evening and morning. I did them all, and gave him the results the next morning.
These showed that we were now getting 0.65, 0.45 and 0.35 Mbps... when the tests didn't just time out.
I was told to expect a response within 72 hours. I then got a text saying to expect a call the next morning (24 hours), which call arrived, only to tell me to expect a call in 48 hours (which is what I was already expecting!!!).
Today we received a replacement 633 - which is hardly going to help, as two 633's have not show themselves as any different. I'll try it, but...
I saw a comment elsewhere about someone whose phone socket had a broken wire in it.... and I just thought I'd have a try connecting the 633 via an alternative socket (using a rather long extension cable). That particular connection had never been checked/changed.
The speed went straight up to 20Mbps.
I went back to the original socket. The speed stayed at 20Mbps. The DSL connection (or rather, VDSL2) had been restarted each time. Previously, I had restarted it a single time, plus it had been restarted when the engineer swapped in his 633.
Now, 45 minutes later, the speed is still 19Mbps. I don't expect it to stay there.
In any case, I have been told that TalkTalk regard anything less than 70% of the speed they have quoted to constitute a fault. 70% of 39Mbps is 27Mbps. We have barely 70% of that figure, and I'm fully expecting it to drop back down to the 0.5Mbps speeds we've been getting for the last few days.
When we sink to 0.35Mbps, we're getting just under 1% of what was promised, and less than 10% of the speed we were getting before fibre.
P.S. Also, the 633 seems completely unable to see our WiFi HP 3050 printer, whereas the old 533 had no problem at all.