Thank you for your uninformed, misguided and unhelpful reply.
Wow! so much drive!
I just risked it and pressed control+alt+delete and the whole thing restarted, but to my surprise the uninstall continued normally.
Really, it happens. It's not unusual thing for CTM.
A few three-finger-salutes later it completed successfully in one go and none (I believe) of my files were lost.
If there's no problems with the hard drive then the restored snapshot of the protected disk or disks is just the same.