As a result of changes introduced relatively recently, and slipped in beneath most people's radar, the point at which a service provider responsibility stops has been shifted back to the boundary of the the property at which the service is provided.
In our neck of the woods the phone lines are above ground and when we had a problem mid-2017 they claimed that the fault was located at point between an imaginary vertical rising at our boundary and the master socket and hence could not be repaired FOC. I argued until I was blue in the face (and arse, for that matter) and got nowhere. I imagine that the same rule now applies to underground feeds.
Yet further evidence, not that any more was needed, that OFCOM exists to protect the best interests of BT/Openreach and their investors and not those of the consumer.
Jon