How slow? - confused

[#1]

I am not sure what is happening but checking my line with 'mybroadband speed' is giving about 2 to 3Mb through the day with occasional 6mb in the evening, sometimes down to less than 2. Bt Test: profile 7000kbps and currently 4785 whilst mybroadbandspeed is giving 2250/321 - just done one reboot of the speedtouch 780 modem/router
Stats are
Link Information

Uptime: 0 days, 1:54:25
Modulation: G.992.1 Annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 8,096
Data Transferred (Sent/Received) [MB/MB]: 6.13 / 71.20
Output Power (Up/Down) [dBm]: 12.0 / 7.5
Line Attenuation (Up/Down) [dB]: 0.5 / 2.0
SN Margin (Up/Down) [dB]: 23.0 / 13.5
Vendor ID (Local/Remote): TMMB / TSTC
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 0 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 0 / 0
HEC Errors (Up/Down): 0 / 0
I normally get between 6 & 7mb but have had this variation for about a week.. Our exchange is very lightly used and others using btinternet are getting just over 7mb. I had the same problem about 6 weeks ago and it took a week or two to come back to normal. We have just had a new line installed and that will be activated next week which should tell us if we have a fault on the 120 metres of cable from the local exchange.
Just this minute done another check and it is now 974/303 - I am going on three weeks hols on Friday so will not bother raising a ticket in case it is the line here.
We had 4 very short power outages over a 30 minute period a week ago - could this have caused a problem?
Mick

[#2]

Can you just confirm - the BT speedtester is consistently giving you much higher "transfer" results then other testers?
This is usually indicative of MTU and RWIN tweaking being required.
If both the BT speedtester and external speedtesters are highly variable throughout the day, this should indicate either high counts of uncorrectable errors (causing retransmits) which your line stats seem to discount, or exchange contention.
B.

[#3]

Hi Barry - It's the 1st BT test I have done for a month so I am not sure. These are the mybroadbandspeed tests
Today 20:59  2644 kbps (331kB/s)  324 kbps (40.5kB/s)  Share
Today 15:42 974 kbps (122kB/s) 303 kbps (37.9kB/s) Share
Today 15:02 2250 kbps (281kB/s) 321 kbps (40.1kB/s) Share
Today 14:55 2413 kbps (302kB/s) 322 kbps (40.3kB/s) Share
Today 13:09 2880 kbps (360kB/s) 341 kbps (42.6kB/s) Share
Today 11:14 4062 kbps (508kB/s) 339 kbps (42.4kB/s) Share
Yesterday 14:30 2793 kbps (349kB/s) 335 kbps (41.9kB/s) Share
Yesterday 11:27 5770 kbps (721kB/s) 272 kbps (34kB/s) Share
Monday 23:18 6814 kbps (852kB/s) 322 kbps (40.3kB/s) Share
Monday 17:35 6751 kbps (844kB/s) 270 kbps (33.8kB/s) Share
Monday 11:40 4054 kbps (507kB/s) 334 kbps (41.8kB/s) Share
Monday 11:38 3232 kbps (404kB/s) 312 kbps (39kB/s) Share
Monday 07:23 7638 kbps (955kB/s) 288 kbps (36kB/s) Share
Aug 5, 17:47 6274 kbps (784kB/s) 327 kbps (40.9kB/s) Share
Aug 4, 08:01 6881 kbps (860kB/s) 343 kbps (42.9kB/s) Share
Aug 3, 17:32 6723 kbps (840kB/s) 309 kbps (38.6kB/s) Share
Aug 2, 00:28 6819 kbps (852kB/s) 319 kbps (39.9kB/s) Share
Jul 31, 07:21 6608 kbps (826kB/s) 263 kbps (32.9kB/s) Share
Jul 30, 22:49 6700 kbps (838kB/s) 306 kbps (38.3kB/s) Share
Jul 28, 10:01 6723 kbps (840kB/s) 311 kbps (38.9kB/s) Share
Jul 27, 09:57 6631 kbps (829kB/s) 306 kbps (38.3kB/s) Share
Jul 26, 09:53 6518 kbps (815kB/s) 341 kbps (42.6kB/s) Share
Jul 24, 06:59 6296 kbps (787kB/s) 329 kbps (41.1kB/s) Share
Jul 23, 07:43 7638 kbps (955kB/s) 357 kbps (44.6kB/s) Share
Jul 22, 07:50 7677 kbps (960kB/s) 225 kbps (28.1kB/s) Share
Jul 20, 13:01 5011 kbps (626kB/s) 323 kbps (40.4kB/s) Share
Jul 20, 11:09 6491 kbps (811kB/s) 243 kbps (30.4kB/s) Share
Jul 20, 00:22 6183 kbps (773kB/s) 312 kbps (39kB/s) Share
Jul 19, 16:28 5788 kbps (724kB/s) 314 kbps (39.3kB/s) Share
Jul 15, 23:29 6564 kbps (821kB/s) 281 kbps (35.1kB/s) Share
As you can see it's normally ok - I am on the Stromness exchange and pals living up to a mile away are getting good results all the time on plusnet.  We are on a modern microwave link connecting us directly into the main exchange and there are only 5 adsl lines in use. The BT eng is coming out to our island next week to activate adsl for a post office line for us on our property. I'll see what speed he gets on that line and get him to check mine for me whilst he is here. Unfortunataly I will be away on hols but he'll ring me and let me know the results. Maybe it will all be back to normal when I get back in 3 week. I have a PC running all the time uploading a few kbytes of data every minute but a slow connection doesn't matter with that.
Mick

[#4]

Checked it overnight and a good bit of difference
Today 07:25  7049 kbps (881kB/s)  333 kbps (41.6kB/s)  Share
Today 00:35 6883 kbps (860kB/s) 353 kbps (44.1kB/s) Share
Yesterday 22:00 2062 kbps (258kB/s) 330 kbps (41.3kB/s) Share