We all sit here, quite smug, and in most cases fairly well informed, so to install the kit in the premises wouldn't be much of an issue, just wait till 18:00 on the day in question, and then on you go, the engineer has done the cab work, etc, etc. The problem is that many get it wholly Pete Tong, Perhaps there is no true NTE in the premises, or is star wired from the BT66, or the NTE is in the loft .........
Back in the previous engineer installed days, 45db or less for a 576Kbps USB modem service, the engineers, as now made sure that it was fed directly from the NTE. There weren't any of the faults we see these days of self install.
You should just look at the design of the 'fibre' NTE faceplate to see it's been created for self-install.