UPDATE: Finally agreed that the lines have been fixed by removal of DLM. Thanks, Alexandra.
The following is intended as a resource for TT tech staff (in the UK). It is not intended as a moan at TT.
For over 3 years (perhaps even 4, by now), my 2 TT broadband services have rarely been stable. One is usually better than the other at any given time, but the only satisfactory service was provided for 6 months by removing dynamic line management from the lines. since January (or so) it has been managing the lines once more, resulting in up to 10-15 drop-outs over a 24-hour period. A connection never lasts through a full working day or night unless a DLM reset has been performed. The line is then stable for around 48 hours before it again deteriorates. A new DLM system is currently operating, which, according to my direct experience of at least 3 TT DSL lines, performs even worse than the original one, due to some obvious misconfigurations.