Gerryb, this is entirely possible, and using smartcards too.
It makes me weep that the NHS doesnt use thin clients and Virtual Desktops.
Putting the windows vs Ubuntu bunfight aside for a minute,
imagine that there are small devices, abotu the size of a paperback book or a pack of cards. These devices are secure, and are certified by the military. They are used by the thousands by trading desks in the City. If the MoD and the banks trust them... why not he NHS?
The devices consume about as much power as a lightbulb, and can be obrained with fanless operation so they are safe in anaesthetic gas environments.
The central IT departmen tof course has to maintain servers running virtual desktops, but this is a mature technology. the data never leaves the data centre. Patches can be applied centrally to the VDI images.
Also USB ports on these devives ar elocked down - you cna only plug in recognised keyboards and mice. A USB stick carrying a virus or used to downloa dpatient data? Pffft. Does not work.
These divices support smartcards and desktop roaming. So all you need to is put your smartcard in the slot. When you move aroudn the department you take the card to the next station and the desktop follows you.
I knwo all this is possible with PCOIP zero clients, and I am sure Citrix also.