This is a bit of an off-shoot from the Part P discussions, but I'd like to relate a few things about our own Self-certification scheme here in New Zealand.
Firstly, let it be known that Self Cert. is in no way a panacea for all that is wrong in the Industry, in fact to a certain extent, it's made things worse.
As in, prior to 1992, we had a good Inspection system here, provided by the Power Board Inspectors, they were friendly and they knew your work standards, testing still happened though.
Now, only where a new switchboard goes in or a change to the Mains or Earthing occurs, does an Inspection happen.
This is where I think that the system falls down.
Nowadays, an Electrician, can do any sort of work in any Installation, without fear of being caught out for unsafe practices, unless of course it causes a fire or shock.
Although Self Cert gives you a lot of freedom, this is being taken too far here.
Self Cert also applies to other Electrical workers here as well as Electricians, like Appliance Technicians and Line Mechanics, but generally, the standard of testing and filling out of Certificates of Compliance has been 100%, with these folk.
(After all you can't erect a set of power lines without someone noticing).
One thing I have noticed since 1992, is the fact that cables no longer get clipped in roof spaces any more.
Only 75% of us Electricians here use COC's and only 90% have Practicising Licences.