Then you are suffering from congestion as you've been repeatedly told. There is nothing we or you can do except nag your ISP or migrate 
I've nagged, and they have requested I do the Tap 2 & Tap 3 BT Speedtester tests.
Only trouble is that my Livebox just won't take "speedtest@speedtest_domain" as a username with password left blank. I've also tried "testing" as a password - but still no go.
my current speeds are still deteriorating by 90% @ peak times; I've just taken my
speed data & router stats:
Download Speed 2408 Kbps
Max Achievable Speed 21000 Kbps
Download speed achieved during the test was - 2408 Kbps
For your connection, the acceptable range of speeds is 4000-21000 Kbps.
Additional Information:
Your DSL Connection Rate :15320 Kbps(DOWN-STREAM), 1104 Kbps(UP-STREAM)
IP Profile for your line is - 13516 Kbps
2. Upstream Test: -provides background information.
Upload Speed 822 Kbps
ModulationType ADSL_2plus;
ATMEncapsulation VCMUX
ModemFirmwareVersion bcm96358_ADSL_PHY_A2pBT009c1.d17d
Status Up
LinkStatus Up
LinkType PPPoA
DataPath Fast
UpstreamAttenuation 119
DownstreamAttenuation 235
UpstreamNoiseMargin 45
DownstreamNoiseMargin 65
UpstreamMaxRate 4293747263
DownstreamMaxRate 18275
UpstreamCurrRate 1104
DownstreamCurrRate 15323
UpstreamPower 126
DownstreamPower 233
UpTime 87063
Stats.Total. Values
LinkRetrain 3
FECErrors 22280
ATUCFECErrors 11745991
HECErrors 52
ATUCHECErrors 953627
CRCErrors 54
ATUCCRCErrors 1141736
The British based Orange tekkie is calling me back within 48 hours, so it'll have to wait til then if no one has any advice to carry out the BT advanced speed connection tests.
My other bitter pill, is I've been billed both by Orange and BT for my home telephone rental and calls, after I transferred it all to Orange (who already was my ISP) 6 weeks ago. After I complained to BT, they pleaded with me to come back, even offered me a cheaper package! I turned the offer down, and requested a refund. Also cancelled my direct debit with my bank - which I've never had to do previously when dealing with BT.