Yes they do Russ - there's a major customer service centre in Manchester, as well as Swansea and Glasgow! The only UK tech support centres are Swansea (for broadband) and Newport (just down the road, for narrowband).
With regard to the problem, as others have said try running the USB scrub ("uninstall.exe" in the Ambit folder, under the Drivers folder on the ntl installation CD), then reboot the PC and plug the USB cable back in. Otherwise, change to Ethernet. A NIC only costs £5 and is far less trouble than USB.
