Dialing from U.S. to U.K. question - wrong city codes?

Sorry to have to post a stupid question, but some days are like that.

We have a Cisco 2851 CME connected to a Time-Warner-Telecom line.

I am able to place international calls to many countries, including
Israel and France. But calls to the UK do not go through.

I called Time-Warner-Telecom for help, but they said that it was a
problem with our router config and that no international calls woul ..
Telecom, Cabling and VoIP continues...