Wholesale speed estimates reduction

[#1]

The issue of changing fibre speed estimates was raised a few weeks ago in the ThinkBroadband forums
http://forums.thinkbroadband.com/fibre/t/4241537-re-wholesale-line-speed-reduction.html
As this is now biting me a little bit I was wondering if any of the PN staff would like to comment on the subject - if they know why the estimates were changed and what issues it may bring up.
It's biting me because I have (I'm pretty sure) a fault on the line that is causing my speed to drop.  When I had fibre installed at the end of last year my estimated download speed was 57Mbps and upload was (expected to be) around 15Mbps - and that was roughly what I was getting for a few months.  The estimate on the Wholesale checker now gives 40Mbps down and 6.5 up.  This is much closer to the 30Mbps and 4.5Mbps I am currently getting (because of the line fault) and is making it slightly more difficult to persuade support the line is not performing as it should (or was).
A reduction in the estimated speed of 33% does seem a bit excessive?

[#2]

Hi there,
I guess they're changing because the technology is maturing and more is known now than it was when it first rolled out - BT are now able to make the estimates more accurate. Bear in mind though that this is an estimate and doesn't really change anything as regards the line or the speeds you'll see. We also don't raise faults based on the estimate, however if you were seeing one speed before now and your current speed is less than three quarters of that we can raise a fault based on that? Not sure if that helps but I hope so.