gas path
for a practical reply.................If you go with BT, who are chasing prices down, as mixture points out, along with plusnet, their "cheaper" brand, then, if all goes well, then it will be fine.
Mixture and others point out that if you have problems, though, BT is an often impenetrable bureaucracy, with too much IT help outsourced to script readers in India, who do not help as they are neither trained nor empowered to help.
As I pointed out above, their inept bureaucracy might allocate the wrong engineer to "solve" any problems........this is frustrating when you have to stay home to let them in.
So you can go with BT, and fingers crossed, all will be well. If it is not well, be prepared for some truly average service. As othewrs have said before, if the service is bad, write to the CEO and/or the Chairman, to get their support units on the job.
I am 1 km from the Green box which has fibre. I get 46 mega whatnots, which is very impressive.......I think I get that because I have a newish copper cable for the last 100 yards.