did you bother to read my earlier post? regardless of contention, my line is capable of 135MB and I'm synced at 80/20 so the point I'm making is that my speeds are rubbish for what I can achieve. trust me this is NOT a contention issue as the BTO engineer told me here was plenty of headroom left in the cabinet. sky are incompetent. there is plenty of evidence of it on the sky and skyuser forums.
Line being capable of 135MB is irrelevant as Sky do not offer this speed - you even say you are synced at 80/20 which is their top speed.
Therefore if your throughput is less than 80/20 it will most likely be due to one form of contention or another, whether that is at the cabinet or further in.