Why isn't my download speed increasing ?

[#1]

I'm puzzled.
After much testing and debating with various people I've got the various factors that I thought were relevant to download speed looking reasonable, see below for my router stats and latest couple of BT Speed test results:
2010-07-14 13:30
Download speedachieved during the test was - 3774 Kbps
For your connection, the acceptable range of speedsis 1000-7150 Kbps.
Additional Information:
Your DSL Connection Rate :7936 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 4000 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is - 18.6:20.88:60.52 (SBE:NBE:PBE)
These figures represent the ratio while sententiously passing Sub BE, Normal BE and Priority BE marked traffic.
2010-07-14 20:00
Download speedachieved during the test was - 3513 Kbps
For your connection, the acceptable range of speedsis 1000-7150 Kbps.
Additional Information:
Your DSL Connection Rate :7936 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 6500 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is - 17.85:29.63:52.52 (SBE:NBE:PBE)
These figures represent the ratio while sententiously passing Sub BE, Normal BE and Priority BE marked traffic.
DSL Connection
Link Information

Uptime: 0 days, 19:52:42
DSL Type: G.992.5 annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 7,939
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 6.00
Output Power (Up/Down) [dBm]: 12.0 / 20.5
Line Attenuation (Up/Down) [dB]: 22.5 / 39.5
SN Margin (Up/Down) [dB]: 19.5 / 6.5
Vendor ID (Local/Remote): TMMB / TSTC
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 12 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 261 / 0
FEC Errors (Up/Down): 208 / 0
CRC Errors (Up/Down): 208 / 19,148
HEC Errors (Up/Down): 2,051 / 15,166
My sync speed is reasonable, my profile speed is OK, my SRN figure is good and my attenuation figure is OK.
So why isn't my download speed increasing ?
I've got the router plugged into the test socket and nothing else plugged in, so what am I not understanding or missing ?

[#2]

I think I can see the reason
At 13:30 today you had an IP profile of 4,000kbps
At 20.00 today it was 6,500 kbps
If you go here https://portal.plus.net/my.html?action=data_transfer_speed it probably still says Current Line Speed 4,000kbps (it can take 12 hours to catch up)

[#3]

I'm testing the exchange to see what profile you're currently on, then will update our side to match as we still have you on a 4000kbps profile...
Edit: I've now increased your profile to 6500kbps, if you don't see an increase in throughput then reboot your router.