Thanks, again, but still the update is borked.
The eject command "udisks --eject /dev/sdf" now works. However, attempting the update of the MKK .bin file does exactly the same, ie at 1 block in the progress bar it terminates and reports that the update was unsuccessful.
So I have now tried every combination of these:
- Update_mkk-20141129-k3w-B008_install.bin (Menu-Settings-Menu-UpdateYourKindle)
- Update_mkk-20141129-k3w-B008_uninstall.bin (Menu-Settings-Menu-UpdateYourKindle)
- KUAL-KDK-1.0.azw2 (Right click - Open)
- Plugged into USB of Ubuntu (ejected through command line using 'udisks --eject')
- Not plugged into any USB
- WIFI Enabled
- WIFI Disabled
- Unregistered
- Registered (excl plugged into USB)
Just to confirm my serial starts with B008 and it is the kindle keyboard wifi model.
Again, the Kindle update from 3.4 to 3.4.2 using the same procedure works fine. Is there any possibility that the two .bin files for MKK are corrupt? 
They have cleanly extracted from "kindle-mkk-20141129.zip"
Also thanks for your patience, especially on the detach/eject command. I should have tried that.