The vast majority of standard house phones or cordless multi-handset phone systems - sometimes referred to as DECT phones - will work perfectly well when plugged into a VoIP adapter (ATA). Put simply,
if your existing system works by having the main base unit plugged into a single BT phone socket, then it will most likely work when plugged into a suitable ATA adapter. This is also by far the easiest and most cost-effective way of getting set up.
Alternatives include VoIP-enabled DECT base-stations, routers or phones, all of which can be configured to work with your service using the settings provided, however it's worth checking compatibility
of all components before investing in any new equipment.
Note that having phones plugged into different BT extension sockets will no longer work, as the copper telephone wiring and sockets in your premises no longer play any part in the phone connection.