I can't give you the definitive answer on this. However I tested my speed last night as follows:
Down = 2956.16 Kbps Up = 378.82 Kbps
I switched off my Router for an hour tonight due to the storms and just tested again at:
Down = 6357.31 Kbps Up = 378.77 Kbps
That speed is the 3rd highest recorded over about 3 months.
I apprecaite that line contention last night might be the reason for the relatively slow download speed but it's up pretty high now.
I'll be interested to know the answer on this.