Are you saying there is no mains power where the Openreach engineers have left the cable or where you would like to site the hub? The hub requires mains power to operate.
If there is no mains power at the distant location you have no options open to you. You can't extend the telephone line as there will be no power for the hub and you can't site the hub at the near location and extend Ethernet as there is no power for the device you intend to extend to and Ethernet won't work over that distance in any case. If there is mains at the distant location you can extend the telephone cable using preferably Cat5/6E cable.
See edited post above, but why didn't you specify the location of the master socket in the first place?
Hi, yes it's a by business connection. There is no mains power where the engineers have left the cable but there is mains power 300m as the crow flies or 500m away from the cable where the hub will be located
This is actually the residential forum. As you are paying for a BT Business connection, Openreach should fit the master socket wherever you specify, as its part of your contract.
Most businesses need a connection at a specific part of the building, so the installer will be expected to fit it there.
You would normally specify the location of the NTE, as part of the order process. Did you do that?