Last weekend we had the chap come to swap out the BT modem on our fibre. Fibre is with Zen internet.
Prior to this, we were getting ~32 meg out of it, according to the thinkbroadband and several other speed testers.
After he went, it had dropped immediately (10 mins after he left) to 18 meg. "OK," we thought, "it needs a little think."
But a week passed and it's no better. We spoke to Zen yesterday about it. They got us to run the BT speed tester, which reports 36 meg. I'm not sure exactly what that tests or how. Anyway, we're still only getting 18 meg as far as we can tell, from 4 testers on various continents, and from the reported speed of files being downloaded. It is noticeably slower than before, when we used to download a 30-min podcast in ~30 seconds, and now it's ~50.
Zen also took the Netgear router out of the equation by connecting us briefly directly to that BT modem. Still 18 meg. At this point they told us that since the BT checker reports 36, BT won't touch it or see it as a fault. Game over, although they've turned on the ping response in our router to watch it for a couple of days.
Taking matters into our own hands, we've also swapped the wall-to-BT-modem cable with one from next door's house (no change). We took our new BT modem to a friend's house (who gets ~34 meg out of his) and tried it there, and his speed was unchanged so it's not the modem either. We get about another 0.5 meg out of it if we unplug the phone from the same socket, but that's all. There's no internal phone wiring in the house from that socket, and we're not using wireless off of it either. Just wall-master socket-modem-router-single PC, ethernet-wired. It's no different if we have the rest of the house network plugged in, to be fair.
As far as I can tell, this leaves either a fault in the master socket, or something occurred when that modem was swapped which has got something stuck somewhere along the line. As I pointed out to Zen, it's a huge coincidence that this happened immediately after the engineer came.
If anyone has any ideas of anything else to try, or something to tell Zen to do, we would be most grateful. BT fault or not, it seems obvious to me that with 36 meg being "delivered" but only 18 meg being "useable", something somewhere is blocking 50% of our bandwidth.
Open to suggestions!