Excerpt from Service Note:
"Whilst booted from the external firewire hard disk it was possible to examine the internal hard disk and the main user data and parts of the OS were not present.
The powerbook was then rebooted from it's internal hard disk - at this point the powerbook exhibited a kernel panic (this would be expected given that parts of the OS were observed to be missing).
After less than 1 hour's use the powerbook began to freeze when booted from CD, internal HD and external HD - this suggested a logic board problem."
So, sixteen weeks after I reported my PowerBook's screen broken to our IT department it's finally fully repaired and back in my grubby little hands, ready for much reinstallation fun. Now that's service for you.