Erm, plugged into the Test socket the speed has now increased to 13Mbps!
That's rather better - and it will probably feel better when using computers too.
Plugging back into the Master Socket with Cordless phone/ Sky box (everything in house) unplugged it goes back down to 4Mbps...
If that happens, the usual suspect would be the ring wire (on connection number 3) that could be injecting extra noise. Pulling this out would probably help, or using a proper VDSL faceplate filter instead - which would keep the ring wire connection entirely separate from the VDSL socket and signal.
You can buy the VDSL2 faceplate, and install it yourself - it fits between the existing faceplate and the existing backplate, giving you an extra socket to plus the modem into.
Even though BT will have sent Openreach out next week will they charge us as it's an internal wiring issue??
The ordinary answer would be, yes, an appointment to fix something on the internal side would get charged.
However, you are caught in an interesting position here... BT Retail chose to sell you a self-install product, and it hasn't installed well enough. It is BT that chose to go with a cheap version of the installation, and in your case it hasn't paid off.
When the engineer comes, he will (almost certainly) only do what the engineer would have done for other types of installation - which is to test the line, put a VDSL faceplate on, and test again. It is what BT Retail would have asked Openreach to do if you had ordered Infinity 2 - but you were never given that option.
If you could have ordered a couple of years ago, you would certainly have had an engineer attend, and perform these steps, as self-install was not an option.
Morally, this ought to go down as a repair after a failed installation, but do Openreach really see it that way? Would they still charge you for that? I'm not entirely sure - and you probably have grounds to try to argue your case if they do.
Whats the next step?
Choose between
- cancel appointment, and fix it yourself
- leave Openreach to attend, and gamble as to whether they will charge you
It is entirely possible that there are other issues with the line, that could be fixed by the engineer's attendance. However, with the HH5, you don't really have access to the full set of line stats to be able to tell if that is a possibility.
Note: Don't do too many more unplugging & plugging-in of the modem in one day, as you don't want to trigger DLM. If you do want to make more attempts to try things out, the best practice is to first power down the modem while it is still plugged into the phone socket, and to then wait at least 30 mins before plugging the line back in and powering back up.