Similar nightmare happened with my brother. Signed up for fibre in August meant to be installed September 10th, nobody came. Then after 6 promised call backs which they failed to keep I phoned up and went through 2 hours of hell and got a new appointment for the 23rd September. BT don't come again.
Called up on the day to check as well, was told they're on their way. Called back after 6, was told the appointment was cancelled the day prior and nobody knows why. Called back next day for the promised notes from the BT engineer, nothing. Then the case went to CEO team... they called friday just gone, a guy is dealing with the case, direct number etc call you next week to arrange compensation and install.
Brother at home Monday (yesterday) BT man knocks at the door (no idea they were coming) hear to install your broadband, activated the phone line had no idea we should be having fibre, made some odd excuse about another man doing the fibre in the street then it will work (no modem so it won't will it BT)... nobody came back.
Called the guy in CEO team at Talk Talk, brother paid for the 2 days taken off work for missed installs, upgraded to large fibre for same price as regular and given £50 credit on the account... (I'll believe it when I see it at this point)
Currently now waiting on a phone call today to find out why a BT man just appeared yesterday and why in gods name he didn't install the fibre. It's almost crazy that it's had to go all the way to the CEO team just for someone to come and install fibre broadband for a new customer.
In short, Talk Talk have THE WORST customer services (unless it's the CEO team) but from past experience their provided broadband is pretty good and cheap... I guess the cheap just means if it goes wrong, it REALLY goes wrong.