Having uploaded the UK specific XML file, I've been tearing my hair out trying to work out why calls coming in on the PTSN (ie BT) line of my OBi110 were ringing the phone once and then dropping the call. The caller still heard the ring tone and the call itself was never being terminated.
Fortunately if I reset the system so that everything was for the US market, the phone rang as it should (with US ring tones) so I knew that the issue was one of the UK specific settings.
It turns out that the setting for CPCTimeThreshold in the Physical Interfaces | Line Port section is very sensitive. The default/suggested UK setting of 9 (9 milliseconds) is far too low. Occasionally it worked if set to 10 but not consistently. I've currently set it to 20. It worked happily with the default of 450 so I've got room to play with!!