From 6Mbps to 47Kbps in a heartbeat

Question

This is not a rant because frankly I don't have the energy for it.
I have now been a BT customer for 14 days and I wont even bother going into the utter mess BT made of getting me online after giving them over a months notice of moving into our new house. 
The connection was reasonably stable at around 5 to 6 Meg until 5 pm on Monday of this week when it dropped like a stone to 47Kbps measured using the BT online tool. I waited a day to see if it was a temporary blip and then made the mistake of calling 0800 1114567.
They stepped me through the whole wired / socket scripted thing. They did a line test and got 35Kbps (or so they said) and told me it was being escalated to the 'Advanced Team' who would contact me at 6 p.m. That seemed weird but hey ho.
No call at 6 p.m. so I waited until 6:45 and called them back. Back through the script again and I would need to be transferred to mobile broadband. I thought that was odd but maybe I miss heard? Nope, Mobile broadband asked me about my dongle and eventually said 'Im sorry you shouldn't be speaking to me I'll transfer you'. 
Back to the script again and now I need to be jacked into the engineers socket. It means I have to drop the call but they'll call back (I wish I had a mobile signal here now) in 20 minutes.
No call back and I wait 45 minutes just in case. I call them back and guess what? Yep, the script again and I'm told to order an accelerator. As I only have one socket that will do nothing according to the online ordering so another red hearing. Oh yes, they'll monitor the line.
I'm not happy now so I call back. Yeah the script etc and here's where it gets good. You need an accelerator, we need to take contol of your machine remotely so we can change settings in your hub (thank god the connection was so bad they couldn't connect) and finally are you using an Anti Virus programme? Yes says me, being all proud of my vigilence its AVG I've used it for years. You need to remove that its slowing your connection down. But my wifes mac is the same and that doesn't use AVG. No answer to that just 'we'll monitor the line'.
I had tweeted something pretty filthy about BT in the mean time and BTCare responded. I have now filled out one of their requests for assistance and I only hope they will do something.
However, the broadband call centre is something to be believed and I flatly refuse to use it EVER again.
If that was a rant I appologise.

Answer 1

Hello I'm afraid that on here we do need to go through a few diagnostics before directing you onto the mods, but if someone from Twitter has already contacted you then I would possibly leave it in their capable hands?
Can you please post your ADSL stats by following this direct link; http://192.168.1.254/ and go to A-Z (top right) and then ADSL Status and post everything including Line Attenuation, Noise Margin, Connection Speed, Errors etc...
Also we need a speedtest just to have a look and make sure everything's okay? Use this link http://bit.ly/uViAXN and post all the required info Throughput, IP Profile etc..). If that one doesn't work then try this work around link http://bit.ly/tIPNYA .
Run a line test to determine if or not it is an external problem: http://goo.gl/J25w8
Lastly for now, call 17070 and Press Option 2 for the Quiet Line test and where possible use a corded phone as DECT handsets can pick up electrical interference?
Are you connected Wirelessly or through a cable?
Regards Edd
Check your Line
BT Speedtester