This is what you need:
Otherwise, if you get a Smart Hub 2, I believe existing phones plug into the dedicated green port on the back, assuming you can get close enough to plug in directly:
If you are using multiple corded phones you need to buy a digital adapter for each one, or talk to BT about getting some Digital Voice handsets that connect directly to the Smart Hub 2 wirelessly (the hub contains something called a DECT base station).
More instructions relating to Digital Voice are here: https://www.bt.com/help/landline/digital-voice-migration
I have no more ports left on my BB Hub. Is there a multi port adaptor or similar I can use to connect my phone for the digital voice change over.
@Reghughes Digital voice does not use any Ethernet ports, your phone connects to the phone socket on the back of the Smart Hub 2.