I'm with BT and am about 3 miles from the exchange. I get 2-3MBs on an estimated 2MB line whilst some of my neighbours were getting less than 1. We all shared the same line to the local telegraph pole which then split 6 ways to each of our houses. For some reason my supply cable is a newer fatter screened twisted pair of 22AWG. The neighbours wires were older and narrower (24 or 26AWG)......prime candidates for a poor line speed. Fortunately it was an easy fix to replace the supply into their properties from the telegraph pole.
I'd always suggets looking at that as a suggestion.