It looks like another "stuck at 10Mbps" problem. They do seem to be cropping up quite often.
I wonder if that's just the line characteristics, the OP is getting pretty similar performance to myself , 45 download and 8.9 upload. BT Infinity unlimited is always the openreach 80/20 product. The BT Infinity option 1 with 40gb usage is the 40/10 product.
If any interest here are my stats.
# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 2
Max: Upstream rate = 9562 Kbps, Downstream rate = 54772 Kbps
Path: 0, Upstream rate = 10497 Kbps, Downstream rate = 48945 Kbps
Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 9562 kbps 54772 kbps
Actual Aggregate Tx Power: 5.3 dBm 12.5 dBm
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 6.2 33.2 49.4 N/A 15.9 40.8 61.6
Signal Attenuation(dB): 6.2 32.0 47.3 N/A 15.9 40.8 61.6
SNR Margin(dB): 5.9 6.0 5.9 N/A 5.2 4.9 4.9
TX Power(dBm): -4.2 -9.4 4.7 N/A 9.4 7.7 4.9
James BT Infinity 2 19/09/2012 - Estimate 44.6/6.5 - Install 52/12 - Actual 46 / 8 Mbps
Huawei VDSL -> Draytek router -> Apple Airport Extreme -> Belkin Switch -> Windows/Mac/Linux/NAS/Phone
13 years of broadband - 1999 ntl:(512k/1M)/BTbusiness(2M)/Metronet(2M)/Bulldog(8M/16M)/BE(19M/16M)/BT FTTC(46M)