A while ago I was told by O2 that this was not supported and would never be switched on for O2 customers, if you have also been told this then its a load of rubbish!
Today I checked my sync on my router (after I had upgraded the firmware) and noticed this
> adsl status
--------------------------- ATU-R Info (hw: annex A, f/w: annex A) -----------
Running Mode : ADSL2+(G.992.5) State : SHOWTI
ME
DS Actual Rate : 12741000 bps US Actual Rate : 1145000 bps
DS Attainable Rate : 12784000 bps US Attainable Rate : 1145000 bps
DS Path Mode : Fast US Path Mode : Fast
DS Interleave Depth : 160 US Interleave Depth : 1
NE Current Attenuation : 34 dB Cur SNR Margin : 6 dB
DS actual PSD : 18. 3 dB US actual PSD : 12. 2 dB
ADSL Firmware Version : 232201_A
-------------------------------- ATU-C Info ---------------------------------
Far Current Attenuation : 17 dB Far SNR Margin : 6 dB
CO ITU Version[0] : 00004244 CO ITU Version[1] : 0000434d
DSLAM CHIPSET VENDOR : < BDCM >
Just a heads up for anyone who has also been told that interleaving needs to be switched on.