yep! it's O2 pay monthly (Premium).
As you correctly said Oranged it shows G.992.3...I'll see what O2 gotta say about this !
I'm on the same O2 package with almost the same attenuation as yours using O2's TG585v7 on firmware 8.2.7.7 (the very latest)
Here's my stats :
DSL Type: G.992.5 annex A
Maximum Bandwidth (Up/Down) [kbps/kbps]: 1,326 / 12,412
Bandwidth (Up/Down) [kbps/kbps]: 1,321 / 9,950
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 0.00
Output Power (Up/Down) [dBm]: 12.0 / 19.0
Line Attenuation (Up/Down) [dB]: 19.5 / 38.5
SN Margin (Up/Down) [dB]: 7.0 / 6.5
Vendor ID (Local/Remote): TMMB / BDCM
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): 29 / 986
CRC Errors (Up/Down): 29 / 0
HEC Errors (Up/Down): 15,846 / 0
As HPsauce says, get your wiring sorted first otherwise if O2 get BT involved it will cost you as everything is pointing to the old wiring+lineboxes in your property.