Thanks - I still have no idea what your graphs are telling me :-)
Perhaps you could post a couple of examples of what you already have for us to have a look at.
My line isn't unstable - it will quite happily stay at the current speed and show the potential uncapped speed unchanged from the moment it first syncs. Would multiple days really make much difference ? No problem in collating several days worth here, but tricky at my neighbour's where I'll need to resite the modem.
That really is unusual.
Potential Uncapped Speed (Attainable Rate) usually fluctuates over every 24 hour period, roughly in line with changes in SNRM.
SNRM is usually at its highest at around 2pm & at its lowest at around 2am for ALL connections.
The scripts can be very quickly set up to collect connection stats, completely unattended, every minute 24/7 until stopped.
It only takes a few seconds to set them up for automated data harvesting.
The BT engineer has already told me there is an issue - it's just how can I effectively get it resolved. I'd be happy to have the pairs of my 2 lines swapped knowing full well my other line is in tip top condition. I could then discard the second adsl line completely.
Did the engineer mention the specific nature of the issue & did he mention the reported line lenghs for yours & your neighbour's connections for comparison purposes (obtainable from his test equipment)?
The onus of proof is on the end user & without an unlocked modem & factual records/graphs that is almost impossible.
As your connection is apparently "operating within acceptable limits", the chances of getting anything done would appear almost non-existant (unless you were able to provide proof of an issue).
Even with proof you would face an uphill struggle.
I have been told a number of times that my connection is satisfactory & all line tests are O.K.
Without ongoing graphical proof to the contrary, I could well have been stuck with sync speeds of 15Mb or so as that is still "within acceptable limits".
Finally, who are your respective ISPs?
Some ISPs are more receptive to trouble-shooting than others.