That's because BT Wholesale probably have a much larger backhaul out of the exchange compared to LLU Providers (I'm NOT entirely sure about this but its quite likely) and the backhaul for BTw products is likely upgraded when FTTC is installed from an exchange.
Sky have to upgrade their Backhaul and equipment in exchanges before they can offer Up to 80Mbps to ensure they can provide a good enough service. If they don't, it could bring congestion issues.
Until Sky give your exchange the all clear for 80Mbps, you won't be able to order the 80Mbps product.
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Downstream Upstream
Connection Speed: 24276 kbps 1211 kbps
Line Attenuation: 16.5 db 6.4 db
Noise Margin: 1.1 db 6.2 db
Edited by chris6273 (Thu 10-May-12 19:38:23)