Thanks for your reply goslow, however with regards to this:
VM will install a phone cable running from the location of the VM hub to the location of your existing phone socket.
They disconnect your existing phone socket from the old line coming in from the street (so as to avoid feeding the connection from the VM hub back out into the street again). The new phone cable connects the phone socket on your hub to the existing phone socket.
When the phone socket on your hub is linked to your existing phone socket, that phone socket is then used as an extension socket linked to the back of the VM hub.
Alternatively, for a wires-free solution, see if you can get an additional satellite phone handset to go with your existing cordless system.
Move your cordless base station upstairs next to the hub and provide another power socket by means of a power splitter socket. Then use the extra satellite handset where the base station used to live. Most cordless systems allow full control of the base station from a satellite handset so you don't actually need to be next to the base station to see missed calls, pick up messages etc.