Just want to help people who have this problem and have been told, or have been led to believe, that it is due to an incompatibility between their handset and the router/hub. It isn't!
I've had a Superhub3 installed and with the phone now directly plugged into the router (no more separate BT sockets) I could ring out but not receive calls.
Many phone calls later I was told my handset was 'incompatible' and I spent many hours trying to get guidance on what 'incompatible' meant and where to buy a compatible handset, including buying (and returning) a new handset.
Fortunately my neighbour has the same hub, so I went next door with my phone, plugged it in and proved conclusively that my phone was fine.
VM now acknowledge that the fault is theirs and it will be fixed by this afternoon - fingers crossed