Where I work we use BT as a partner to supply ISP traffic as well as the Wide Area Network - over the past 4 weeks (although we have paid for an 'exclusive' 160 ports from BT) no connections available (we only had 3 people in working) and average ping times of 500ms to a Cat A site in the UK.
Reponse from BT "we are not aware of any problems". Sent them a note with a trace report and that changed to "we are currently investigating........"