The Post Office released me from an ADSL contract because their backhaul via Talk Talk
I think I may have advised you on these forums about your problem at the time...
The exchange in question has Talk Talk LLU so different .....yes this would be a (Wholesale) Talk Talk business line.
Just been back on site and noticed the incoming line to the master socket is cable tied for a few 10's of metres to a 3 inch square metal duct (mains electric by the looks of it). The building is an ex-agricultural warehouse; I could not find the point of entry of the phone lines, it may be a locked side room (landlords office).
I am up loading to MyDSLWebstats under the username snowPSF.