BT Issue Routing to USA

It looks like some of our customers using BT internet as an ISP are having issues routing to American Sites. UK Sites and Servers seem uneffected, however domains that have their nameservers in the US will also have issues remotely connecting to the office. This can be temporaly fixed by using the direct server IP. This looks to be a local BT issue as other customers on Zen connecting through a BT line are uneffected.