Lower speed after switch to PlusNet from BT

[#1]

I have been with PlusNet for nearly a month now and I'm wondering why the broadband speed is not closer to what it was before, I have a months worth of stats before the switch from BT which were consistently higher than it is after the switch
This is the before stats
ADSL Line Status
Connection Information
Line state:
Connected
Connection time:
5 days, 00:26:17
Downstream:
12.58 Mbps
Upstream:
1.118 Mbps
 
ADSL Settings
VPI/VCI:
0/38
Type:
PPPoA
Modulation:
G.992.5 Annex A
Latency type:
Interleaved
Noise margin (Down/Up):
2.7 dB / 5.8 dB
Line attenuation (Down/Up):
33.9 dB / 18.5 dB
Output power (Down/Up):
20.4 dBm / 12.4 dBm
FEC Events (Down/Up):
384919948 / 565
CRC Events (Down/Up):
376984 / 66
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):
4149239 / 44
Error Seconds (Local/Remote):
19523 / 21
This is after
ADSL Line Status
Connection Information
Line state:
Connected
Connection time:
2 days, 23:32:20
Downstream:
10.93 Mbps
Upstream:
1.109 Mbps
 
ADSL Settings
VPI/VCI:
0/38
Type:
PPPoA
Modulation:
G.992.5 Annex A
Latency type:
Fast
Noise margin (Down/Up):
5.3 dB / 6.4 dB
Line attenuation (Down/Up):
33.9 dB / 18.8 dB
Output power (Down/Up):
20.6 dBm / 12.3 dBm
FEC Events (Down/Up):
0 / 0
CRC Events (Down/Up):
26132 / 89
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):
62707 / 71
Error Seconds (Local/Remote):
12426 / 33
This is the current BT Wholesale test
Telephone number:
01933651***
Phone exchange:
IRTHLINGBOROUGH
Estimated line speed:
11Mb (This may vary between 7.5Mb and 15Mb) - Checked on 2015-08-06 12:00:42
Current line speed:
9.8 Mb
BT Wholesale Broadband Performance Test
Download Speed (Mbps)  9.52
Upload Speed 0.93
Ping Latency       (ms) 52.75
 Download speed achieved during the test was - 9.52 Mbps
 For your connection, the acceptable range of speeds is 4 Mbps-21 Mbps.
 IP Profile for your line is - 9.87 Mbps
Upload speed achieved during the test was - 0.93Mbps
 Additional Information:
 Upstream Rate IP profile on your line is - 0.83 Mbps
Will the speed improve over time or is this it, I haven't changed anything my end, the line is the same, I take it that the exchange equipment is the same so why the drop in speed ?

[#2]

There are some minor differences in how the ADSL is operating which may account for the speed difference.
Before: 3 dB target noise margin, interleaving on
After: 6 dB target noise margin, interleaving off
(I have assumed the target noise margin in each case is close to the downstream noise margin shown in the stats.)
The lower target noise margin allows more bandwidth, but may make the line less stable.
Interleaving on increases stability, doesn't usually increase or decrease the bandwidth much, but also increases latency, giving higher ping times, which is worse for gaming.
The target noise margin, and interleaving being on or off, are usually managed automatically to achieve a balance between speed and stability. It's possible interleaving on allowed the line to be sufficiently stable with a 3 dB margin, but with interleaving off, it needs a 6 dB margin to remain stable. If it's been about a month, it probably won't get any faster by itself. Plusnet can change the interleaving and target noise margin settings, although depending on how they do it, the automatic DLM system may change them back.
That said, I suppose your speed, both before and after, might be a little lower than what could be expected for the line attenuation, but not by much. There may be room for improvement, depending on what kind of master socket you have, and if you have any other telephone sockets, how they are connected.

[#3]

Well, I'm well unimpressed after the switch to PlusNet from BT taking over a month, no internet access for 12 hours on the day the switch occurred and broadband speed gone from 12.5 Mbps to around 9 Mbps, no changes my end, same line so I presume the same exchange equipment, I can't see why the speed should change at all as the bit that matters, the connection from the exchange to the router didn't change at all, the reality doesn't seem to match the advertising blurb.