Line rate always changing / Hub resetting itself

Question

Hello
For the past 6 or 7 months we have seen dramatic fluctuations in our Broadband download speed. This change always comes about as a result of our our Home Hub 4 seemingly restting itself: we have normal internet use with a blue light on, but then the Hub will flash orange for a while and come back with a blue light. There is no pattern regarding the time of day; it's completely random.
I've been informed that a resetting connection will only inform the exchange that there is a problem, thus prompting the "IP Profile to be reduced" to make things stable. Surely then this isn't supposed to be happening?
There was a time when we would always get around 2.7 - 3.3 Mbps line rate, which is the best we could expect for our area and the distance from the exchange. The download speeds associated with that were good enough for us, but we can never seem to get that now.
The Event Log will report the process described above as: 'Failed to Resolve Host' and, once the connection is re-established, the line rate will usually be lower than it was before. As an example, a line rate of approx 2.3 Mbps will drop to about 1.3 Mbps. Sometimes this process will return a slightly higher line rate!
This happens approximately once every day, but the line rate is never the decent 3 Mbps we used to get...Sometimes I get lucky by manually resetting the Hub and the line rate will be 2.5 Mbps...but it isn't long before it resets itself and, again, we have about 1.2 Mbps.
Current event log:
12:24:27, 18 Sep.
( 97.940000) DSL noise margin: 5.90 dB upstream, 6.00 dB downstream
12:24:26, 18 Sep.
( 96.910000) DSL line rate: 934 Kbps upstream, 1315 Kbps downstream
12:24:11, 18 Sep.
( 81.000000) CWMP: session closed due to error: Could not resolve host
In the last month there was a small amount of noise on the telephone line (we were looking into it but it appears to have gone), but this line rate fluctuation started long before then anyway. Phone call with the Telephone department team told me there appears to be no problem with the line. We have also had 3 different Hubs during that time, so it isn't a Hub issue. Filters in place and Master Socket is in use. Using the test socket yeilds same problems.
Further questions if anyone is able to answer them:
Besides interference from noise, is there a good reason for the Hub to go through this process and force lower speeds upon us? Is the exchange throttling us or something?
For a period last year we were getting 380 kB/s in a speed test and that was fine to use because it matches the line capabilities that we have always been quoted. I don't understand why we can't have a similar speed now. We don't even get > 300kB/s during off peak times. Is it normal for our DL speed to now be always be about 180 kB/s? We were told during our recent re-contract that there is no longer any capping.

Answer 1

presumbly the previous stats were from the test socket as new stats are just the same
any exchnage problems  http://usertools.plus.net/exchanges/mso.php
http://usertools.plus.net/exchanges/?
http://btbusiness.custhelp.com/app/service_status
http://bt.custhelp.com/app/answers/detail/a_id/15036
http://community.plus.net/exchange-information/
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