The engineer that did a DLM reset on my line last week did say that TalkTalk really do not like arranging engineer visits, they will do ANYTHING to avoid it in fact. It looks like all you need is a DLM reset to remove stuck banding, but an engineer visit is required for that.
In my case, I had a stuck 60M profile for just a month but my ISP (Zen) agreed that it looked like it was stuck and arranged for an engineer visit, and even if they did not find any fault I would not be charged. As part of DLM reset he said he had get all line tests passed before that could be done.
It was interesting that after he did DLM reset the line was on interleave, but he just called up some OR call centre and got them to change the line to remove all interleave - so they do have remote access to at least the DSLAM.
Going back to TalkTalk - I have a 2nd ADSL+ LLU line with them, and after a fault (sync was fine but ppp failing) it took me 4 weeks to convince them to send out an engineer - I had no internet access at all during this time and the only compensation they would give me was a months worth or subscription refunded (the month where I had no access!). Imagine if this had been my only line - I work from home!
TalkTalk are cheap for a reason.........
So unless you get a fault I doubt TalkTalk will do anything.