Fixing the wiring in your house safely is not rocket science (especially in the time of the RCD). Millions of people have been doing it for a long time now...
With respect, not all circuits are protected by RCDs, I think the basic answer at this point is that it is illegal for a non registered person to do electrical work on a fixed installation whether we like it or not.
But as far as I know this stops at the fixed wiring, and as such you can make any thing you like to plug into a GPO without any electrical certification required, which may expose the end user to a far greater risk, particularily with non RCD applications.
The danger is also in renovating etc, as mentioned with the insulation installers, eg it's not hard to put a roofing screw through a wire and leave the roof "live" , (particularily with plastic downpipes) but is not a problem until someone steps off an alluminium ladder.