depends on the status of the line.
if it is disconnected then the previous tennant instructed bt to carry out a cease.
if so - then you will struggle to get out of the £125 part. Openreach charge BT/Sky/Any Man and His Dog £125 to set up a line.
If the previous owner/tennant was an LLU customer then same applies, to connect the wires back up to a new network (BT or any other provider) will cost £125.
Openreach are an independant company owned by BT, they charge the same regardless and the providers pass on the costs. Having said that, some are subsidising the connection fee (eg. BT Retail were charging £30 the other month, don't know if it's still valid).
Good luck anyway.