Just a note to say that the dropped connection issue has been sorted (finally).

It took phone calls to customer service, india (no help

), tech support india (no help

), faults, uk (tried to help - but put me back to TS who were no help), retentions, uk (who promised to help...) and finally the escalations department, uk, who called me to ask why I was leaving, said they would get an engineer to me within 12 hours and when the engineer arrived he said what I had said all along;
It WAS the black terayon modem at fault, so he replaced it.
Total time spent trying to get this issue fixed = over 2 months
Total time engineer spent solving problem = 1 minute
In 10 days time though BT will be installing my new BB service, as I have lost faith in ntl through their inept CS department.