If you look at these cases though, they are in situations where shoddy workmanship has been carried out, and the installations have been left in dangerous conditions.
If you are fully qualified, carry out your work in accordance with the regs, test and issue certificate, then i do wonder if they would actually bother trying to take you to court just for failure to notify, especially if building control found nothing wrong with your installation.
I too am not registered at the moment, and just mainly do maintence work and non notifiable stuff, although i must admit I have chanced my arm a few times and done work that should be notified for friends and family, but made it clear to them about Part P.