Causes of Line Errors?

[#1]

I just wonder what in particular causes lines errors - crc hec etc?
I'm on an error prone line. Crc errors a day are usually around the 5000 mark with Hec errors two thirds of that. With interleaving on it's around two to three hundred. But everything loads fine so it's not a problem.
Why I ask is because a few weeks back I couldn't connect. Around 7pm it would drop then just keep trying to connect. Line would be up thirty seconds or so then just drop again. After midnight it was OK but then it would drop again just once just after 9am.
Plusnet were good enough to send me a new v8 router. I'd been using a single port non wireless speedtouch and also tried a v7 but it made no difference to the disconnects. The problem seemed to clear up by itself after a couple of days before I had a chance to try the new router.
Anyway the dropping problem started up again a few days ago at the same time of around 7pm. The next day I thought I would give the v8 speedtouch (and a new filter) a go. On cue just after 7pm the line dropped only this time the router reconnected OK. But it was showing a phenomenal error rate. For the first time I watched Hec errors catch up and pass crc errors reaching over a million in a few hours. And again for the first time up errors appeared and grew to a few thousand.
While this was going on as you may have guessed pages were very slow to load. I assume that this error rate was the reason behind  the previous routers failure to connect and that the v8 was a lot better in this respect. Then again just before midnight things appear to go back to normal.
After a couple of days things have once again settled down with the line up for nearly three days now.
There is a lot going on in the area. Demolition of a couple of large buildings (around the time of the first problem), gas pipe renewal, putting in water meters down my road, and renewing cables.
But at those specific times of my problem, around 7-11:30pm I just don't know. Maybe as someone said it could be fibre related work at the exchange. Who knows, I just hope it has finally faded away and doesn't come back.

[#2]

In my experience errors are usually caused by interference/noise on the line, though there's a lot of things that can cause that - work in the area, electrical interference etc. Unfortunately there's no easy way to tell what's actually causing it.
Certainly hope it does go away and things stabilise for you soon If not raise a fault and we can get it investigated for you.