ADSL dropping, now almost unusable

[#1]

I had a problem in early Jan with my connection dropping frequently (http://community.plus.net/forum/index.php/topic,147473.msg1299177.html).  It went away after a few days but now it's back and is much worse.  I've done the fault report thing, but when it drops it can take 15-20 minutes to come me back so I'm using 'phone/3G to type this post.  It's got to the point now where it's dropping so often and for so long that I can't do anything. I've tried another router but it makes no difference. 
The router status says DSL is connected but the diags log says "Error ppp0 LCP down".
Help please!

[#2]

Hi and sorry to see that's become an issue again.
Diagnostics aren't showing me what the cause is so our faults guys will be investigating before getting back to you ASAP.
Here's a log of your connections for the past 7 days in case that helps:
<img src="http://community.plus.net/visualradius/generated/image14564089175283.png"/>

[#3]

OK thanks - that confirms what the router log tells me.  The 'phone line went dead for a short while just now, could that be a result of someone running tests at your end?  It's back again now.

[#4]

Yes the full testing we run is intrusive and can drop your phone line for a short time.

[#5]

I've now had a message from Support thus:
We have asked our wholesale broadband suppliers to turn interleaving on on your phone line to try and fix your current broadband problem.
Interleaving is a form of error correction that helps to improve the stability of high-speed broadband. One drawback of interleaving is that it can increase ping times, which may cause problems for online gamers.
We think that turning on interleaving may help with your connection problems. Interleaving usually takes 24 hours to turn on, but can take up to 5 days to take effect.
If you are still seeing problems with interleaving switched on please get back in touch with us. Thank you for your time and patience

Given that the problem manifests itself as a day or so of massive instability every 6-8 weeks with no issues in between is Is this really the right way to try and fix it?  Surely there must be an intermittent fault somewhere.

[#6]

Well perhaps unsurprisingly interleaving hasn't helped. No connection at all for the last few hours (posting via 3G).  This is starting to get tedious. Clearly there is a fault somewhere.
Finally reconnected at 01:17 this morning.