Very slow internet over past few days

Question

Hello
My internet has been fast and stable for a number of years, until Wednesday morning that is. I usually get about 13Mbps downstream and 900kbps upstream, but now it hovers around the 200k-350k mark downstream and 400-550k upstream.
I'm connected to the main socket, which in old style socket with the slot in the middle of the faceplate. I've tried multiple routers, including a new one, and wired/wireless: the results are the same. I've also tried a new filter. There's nothing else connected (and I have no Sky box).
The results of my tests are as follows:
Line state Connected
Connection time 0 days, 21:56:12
Downstream 18,002 Kbps
Upstream 828 Kbps
ADSL settings
VPI/VCI 0/38
Type PPPoA
Modulation ITU-T G.992.5
Latency type Interleaved
Noise margin (Down/Up) 3.5 dB / 7.2 dB
Line attenuation (Down/Up) 22.0 dB / 10.9 dB
Output power (Down/Up) 21.1 dBm / 12.4 dBm
Loss of Framing (Local) 0
Loss of Signal (Local) 0
Loss of Power (Local) 0
FEC Errors (Down/Up) 64755648 / 8
CRC Errors (Down/Up) 880 / N/A
HEC Errors (Down/Up) N/A / 38162
Error Seconds (Local) 465
and
1. Best Effort Test: -provides background information.
Download Speed
0.33 Mbps
0 Mbps 21 Mbps
Max Achievable Speed
Download speedachieved during the test was - 0.33 Mbps
For your connection, the acceptable range of speeds is 4 Mbps-21 Mbps.
IP Profile for your line is - 15.88 Mbps
2. Upstream Test: -provides background information.
Upload Speed
0.47 Mbps
0 Mbps 0.83 Mbps
Max Achievable Speed
Upload speed achieved during the test was - 0.47Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps
This test was not conclusive and further testing is required.This might be useful for your Broadband Service Provider to investigate the fault.
My exchange does not report any errors at all. I conducted an external inspection of my nearest cabinet and all seems OK. I did a quiet line test and can hear no noise on the line.
I hope I've covered everything! Any help or advice would be greatly appreciated.
Best wishes, -Jon

Answer 1

Thanks.
Power supplies -- I've tried different one by trying different routers
Power cables -- ditto above
Central heating pumps -- I have electric heaters (all off)
Dimmer switches -- none
Fluorescent lighting -- none
halogen lighting -- none
door bell power supply -- n/a
speakers -- none
TV interference -- n/a (no TV)
phone chargers -- n/a (in another room)
sky boxes -- none
other satellite receivers -- none
certain types of radio transmitter -- none
microwave ovens -- none
Mains "network" adapters that use home mains wiring to extend your network can kill broadband -- none
Segregate cables away from router cable -- done
check/change your filters -- done, no change
tidy your cables -- done
check your line with a quiet line test -- done
There are no problems reported in my area (or at my exchange).