Cable gauge matters as much as length. Use copper that is 0.9mm instead of 0.5mm, and you can get the same speeds at 2x or 3x the distance. 0.6mm gives an improvement, but not as good.

Thicker copper is in use in some places - particularly where it was needed to get the voice signal back to the exchange ... and the thickest parts of the full run would tend to be in the D-side.

In the end, actual length is irrelevant. It is all about the insert loss, or attenuation. Openreach does have records of the insertion loss between each DP and the parent cabinet, and it is this figure that feeds into the estimation tools. Those records can, of course, be wrong sometimes.

I never posted the final chapter of this saga. A while later, our line had a fault which interrupted voice and ADSL. We had an experienced line engineer on the ticket who called me for a chat, he explained he had fixed three faults between property and the exchange so ADSL was measurably improved, which indeed it is was by 50% or so to around 3MB/sec.
Mysteriously VDSL was then offered on the checker website a few days later with estimated 4MB/sec download.

I purchased this service (from Plusnet) and guess what, I consistently get over 24MB/sec, despite the long line. (ca 1800m)

This is great but I am angry at the runaround I received from BT retail and in particular the Ombudsman service who were not impartial, parroting BTs assersion that the line couldn't possibly work with VDSL..

In reply to a post by gtrman:

I never posted the final chapter of this saga. A while later, our line had a fault which interrupted voice and ADSL. We had an experienced line engineer on the ticket who called me for a chat, he explained he had fixed three faults between property and the exchange so ADSL was measurably improved, which indeed it is was by 50% or so to around 3MB/sec.
Mysteriously VDSL was then offered on the checker website a few days later with estimated 4MB/sec download.

I purchased this service (from Plusnet) and guess what, I consistently get over 24MB/sec, despite the long line. (ca 1800m)

This is great but I am angry at the runaround I received from BT retail and in particular the Ombudsman service who were not impartial, parroting BTs assersion that the line couldn't possibly work with VDSL..

Other factors/upgrades could have been changed that enabled VDSL.

You did back in December http://forums.thinkbroadband.com/fibre/t/4576840-re-...