The BT Voyager 105 is a USB-based ADSL modem and from what I read on various sites, the Mac drivers, although available) are pretty shoddy.
Most UK IPSs supply USB ADSL modems because they are cheap and 99.9% of Windows PCs have USB, whereas not all have an Ethernet network connection.
USB ADSL Modems are generally inferior to Ethernet ADSL Routers so I would 110% recommend investing in one (such as the Netgear DG834).
Ethernet ADSL Routers require no drivers whatsoever, work faster and more reliably than USB modems, and they don't take up a USB port (usually requiring you to buy a USB hub).
Also, many Ethernet ADSL Routers have pretty decent hardware firewalls and VPN capability built-in (the Netgear DG834 has).
So, I would forget about your Voyager and get an Ethernet ADSL Router.
Also look at the D-Link DSL-300T 1-port ADSL Ethernet Modem or the 4-port D-Link DSL-504T ADSL ADSL Modem Router.