20% slower after upgrading to 80/20

[#1]

Background:  
I was on a 40/10 package with 120Gb monthy allowance as a result of being on an old profile when I participated in the FTTC trial.
I decided to upgrade to 80/20 partly because the BT estimator suggested I would get 59/20 and partly for the extra allowance.  This proved a mistake.
These are the last two entries from the fault ticket I raised when the upgrade reduced my download speed.
[quote=Me]
Prior to upgrade I had a stable connection at 37.5/8.3 (stable since FTTC installation)
Following the upgrade I had a stable connection for two weeks at 36ish/12.3
At this stage I believe my profile was 25M-49M Downstream, Interleaving Off - 10M-19M Upstream, Interleaving Off
After the second BT engineering visit and line test my connection was at 30.7/11 and seems to be slowing down
I believe my profile is 20M-40M Downstream, Interleaving Off - 8M-17M Upstream, Interleaving Off
(all speeds from MyBoradbandSpeedtest).
I am not too concerned about uplink speed. Extra is nice but 8.3 was more than adequate. However, a 20% drop in downlink speed is not good. It looks to me as if I would be better off on my original tariff.
I accept that the line may not be capable of speeds greater than the 37.5/8.3 I had originally, or possibly the 36/12.3 achieved for two weeks after installation but both of these are way superior to the 30.7/10.7 it tested at this morning. May I suggest that we try restoring the earlier profile and if that does not succeed I would be happier to back out the entire upgrade.

[quote=CS]
[removed] - BOT - DSL Logged Faults
2:57pm, Thursday 27 Sep 2012
Dear Mr Goddard,
The speed is currently showing as 33Mbps on our testing.
The line profile is not something we can change. This is set by the line management system.
The product can be changed back to the 40/10 package, but this would then come with less usage. 40GB instead of the 120GB you have now, plus there is no guarantee you would get the speeds you had previously.
Please do not hesitate to get back in touch online at http://contactus.plus.net or by phone on 0800 432 0200 or 0345 140 0200 if we can be of further assistance.
Kind regards,
link:csa removed

As you can imagine, I am very disappointed.  My line is clearly able to support considerably higher download speeds (the most important stat by far) but apparently CS cannot change the profile and give me access to them?  I'm not sure how this squares with other discussions here about changing profiles but I feel I have been hung out to dry.  I can either continue to pay a higher price for a worse service, with the minor consolation of increased usage allowance, or I can gamble that 40/10 will give me back a decent speed but at the cost of a massive reduction in usage allowance (40Gb is pretty pathetic if you make any use of catchup TV type services).
So, is there anything that can be done to jumpstart my line and get me back at least to the 36/12 I had before BT did their tests.
[Moderator's note by Adie (Adiewoo) CSA name removed as per Forum Rules]

[#2]

Thanks for posting,
Your ticket is back with our faults team now so I'll make sure someone responds ASAP.
In a worse case scenario I see no reason why you couldn't remain on the current package whilst using a 40/10 connection, however I'm certain we can take another detailed look at the fault for you.

[#3]

Thanks Adam

[#4]

OK, the fault ticket now contains the following:

Quote

Thank you for getting back to us. I am sorry to hear that the speed is not what you would expect from the line. As the line is passing through your exchange it is also subject to the Dynamic Line management (DLM) which is responsible for assigning correct profile for your line. This is monitoring your connection and if the connection is dropping out or there are errors detected the profile is lowered down which will cause for the sync speed between your router and exchange to be lowered down. This is in place as the connection should be stable and error free even thought speed is decreased. If the connection stays stable for period of 10 - 15 days without any errors the profile is increased and you see increase in your speed. This is all done automatically at your exchange and we cannot change profile manually. Unfortunately after the engineers visit the estimated speed for your connection was lowered down due to the aluminium cable on your line and your line is now not showing any issues. I understand that the line was working at faster speed but at the moment there is no fault and we would not be able to investigate this further.

The engineer's visit was on the 19th, so the speed has now been down at 30Mb for 10-11 days.  On the basis of the above I would expect to see some change at the end of this week if not before.  I will reopen the ticket at the beginning of next week if there is no improvement.

[#5]

I posted about this issue on thinkbroadband and no-one from any other ISP is reporting anything similar.

[#6]

Well, after 20 days there is no automatic improvement.  I have reopened the fault report with this comment:

Quote

OK, the line has now been up for about 20 days without any problems and the speed, rather than increasing, has deteriorated further, although not by much. I have a line which is clearly capable of 37.5/8/3 or 35.5/12.3 since it has run at both speeds for extended periods. However, after the last BT visit the speed dropped to 31/11.1 and has since deteriorated to 30/11. I simply cannot accept there is no way to get the speed back where it was when we started this so-called upgrade.

There has to be some way to force the line management system to try a faster speed.

[#7]

Hi leng,
I have spoken with our faults team who are picking this up, I'll keep an eye on the results and you'll be updated once we have them.

[#8]

Speed has now dropped to 29.6/9.9.
I have serious regrets about attempting this upgrade.

[#9]

Hi there,

As Adam said above we could look at moving you back to the 40/10 speeds but leave you on your current account type if you wish? I'm afraid we couldn't really promise it would solve things for you but it might be worth a go.

[#10]

Well, I suppose it is worth a try.  At 40/10 I had a rock solid 37.5/8.3 (measured) transfer speed which is far superior to what I am getting now.

[#11]

Thanks, that's been placed for you and should complete for Monday morning. Hope it sorts things for you, I'll update the fault ticket saying I've placed it too.

[#12]

Well, that has pushed me back to 32/8.3, which is an improvement over the 28 down I was getting before the change.  Hopefully the downspeed will ratchet up a bit now towards its original 37-38.  I'm assuming rebooting the modem would be a bad idea.  Is it worth rebooting the router or should I just leave well alone?

[#13]

If you're to reboot, the best way is to do a soft disconnect. Do this by logging into your router's interface and clicking disconnect then power down your router and modem,  leave for a couple of minutes before powering on the modem and wait for the DSL light to become solid. Then power on your router and login to the router interface and click connect.
Let me know how you get on.