Connection speed slowed to a crawl!

Question

I have posted before about the issue with slow connection speeds.  Well the issue has once more reared its head after a reasonable period of achieving decent speed considering distance from the exchange etc.
Today the connection virtually unusable and when I checked the ADSL line stats downstream had dropped from over 4MBps to under 1 the noise margin had increased to 19dB from around 6dB.  I ran a quiet line test which proved ok
My connection is via an extension and has been this way for a good number of years.  AFAIK there are no problems with the extension after checking filters etc. nothing has changed since installation, but obviously cannot rule out completely although cannot see why a sudden change. 
I turned off the home hub and waited for a minute then back on again.  The comparison below shows changes to original figures only. 
ADSL Line Status
                                                Original                                   Today
Downstream:
                               4.313 Mbps                 2.406 Mbps
 Upstream:
                               448 Kbps
ADSL Settings
VPI/VCI:
0/38
Type:
PPPoA
Modulation:
G.992.1 Annex A
Latency type:
Interleaved
Noise margin (Down/Up):
6.3 dB / 20.0 dB        15.9 dB / 21.0 dB
Line attenuation (Down/Up):
50.1 dB / 31.5 dB      51.1 dB / 31.5 dB
Output power (Down/Up):
19.1 dBm / 12.3 dBm 18.5 dBm / 12.3 dBm
FEC Events (Down/Up):
150 / 0                          0 / 0
CRC Events (Down/Up):
1 / 0
Loss of Framing (Local/Remote):
0 / 0
Loss of Signal (Local/Remote):
0 / 0
Loss of Power (Local/Remote):
0 / 0
HEC Events (Down/Up):
0 / 0
Error Seconds (Local/Remote):
1 / 0

Answer 1

Today I have had a visit from an engineer and my faulty extension(?) has been replaced as has the original BT master socket with a BT ADSL v1.0 filter.
The interesting thing for me was that the engineer asked if we had Sky HD which I must admit I did not think could be an issue but when disconnected the slow speed I had been experiencing increased to Downstream 2.688Mbps, Upstream 448Kbps.  So obviously Sky is taking some bandwidth?
After the new extension and ADSL faceplate the downstream/upstream speed have remained the same (as when Sky disconnected).  I am hoping that speeds will improve over the next few days but was informed that it is possible due to previous issues that the speed has been throttled which may mean it will not recover without me contacting BT directly.  If this is the case how long should I wait?
These are my new ADSL stats:
ADSL Line Status
Connection Information
Line state:
Connected
Connection time:
0 days, 02:53:30
Downstream:
2.688 Mbps
Upstream:
448 Kbps
ADSL Settings
VPI/VCI:
0/38
Type:
PPPoA
Modulation:
G.992.1 Annex A
Latency type:
Interleaved
Noise margin (Down/Up):
15.2 dB / 19.0 dB
Line attenuation (Down/Up):
50.9 dB / 31.5 dB
Output power (Down/Up):
18.5 dBm / 12.3 dBm
FEC Events (Down/Up):
1115 / 0
CRC Events (Down/Up):
6 / 0
Loss of Framing (Local/Remote):
0 / 0
Loss of Signal (Local/Remote):
0 / 0
Loss of Power (Local/Remote):
0 / 0
HEC Events (Down/Up):
73 / 0
Error Seconds (Local/Remote):
2 / 0