A BT spokesperson gave us the following statement:
"... Unlike Virgin, we think the bandwidth we provide our users should be equal for all services and if services like the BBC iPlayer put too much strain on the bandwidth, both ISP's and content providers should educate the users on that issue so that users know when and why they may have to upgrade their account for more bandwidth if it exceeds 'fair use' terms. We always bear the consumer in mind first and have no plans to prioritize traffic from third party companies. We welcome all the Virgin customers who left because of the net neutrality issue and offer 'neutral' bandwidth."
If your on Virgin, sounds like a good time to switch.