Thanks, I gave it a whirl:

Battery level 40 %, continuing.

image [state progress transfer flash speed]
---------------------------------------------------------------------
[x] cert-sw [finished 100 % 1 / 1 kB NA ]
[_] mmc [init 0 % 32768 / 1264659 kB NA ]
ERROR: SU_GET_UPDATE_STATUS_REQ terminated with error code 1: Unknown error

image [state progress transfer flash speed]
---------------------------------------------------------------------
[x] cert-sw [finished 100 % 1 / 1 kB NA ]
[f] mmc [init 0 % 32768 / 1264659 kB NA ]
Fetching error list:
========================================
Update content failed to verify against cert: SW certificate not updated
bb5_rdc_cert_read failed
bb5_rdc_cert_read failed
bb5_rdc_cert_read failed
bb5_rdc_cert_read failed
bb5_rdc_cert_read failed
mmc: sfdisk returned status 1
mmc: Could not exec '/sbin/dosfslabel /tmp/sudmmcrSwITs/internal0p1 "Nokia N9"'
mmc: Unable to remove mount point '/tmp/sudmmcrSwITs/mnt/home': No such file or directory
mmc: Could not remove mount directory /tmp/sudmmcrSwITs/mnt: No such file or directory
[Pipe 1] Finishing in error state with status 1
========================================

ERROR: Failed to flash images
garys-mbp:~ garycalcott$

Very strange, maybe the underlying hardware is just broken?