My house has old, not updated, phone wiring. The incoming phone wire is not connected to a BT Master socket but just connects to an ordinary socket. From there it is connected by a mix of 4 wire and six wire cables to a whole series of other extension sockets.

The incoming wiring has 4 wires: green, orange, brown and blue. How does this correspond to the modern green/white, blue/white, orange/white, white/green, white/blue and white/orange cabling?

Are BT supposed to fit a modern master as I understand I shouldn't be connecting their incoming cable myself? At the moment there appears to be no proper BT termination between the internal wiring and their line. Will they expect me to pay, is their a standard charge for such an update and how do I arrange it?