What does he mean 'isn't allowed to sign a cert?'
That statement right there tells me everything I need to know about this 'sparky' and the level of knowledge he has of his profession. Sadly, its all too common now, too many people like this going around doing work with probably only half the knowledge they need to do the job.
I worked on a site last year installing street lighting. The length of cable runs were into hundreds of metres and we were installing 6mm swa. A 25 year old, apprentice trained, JIB reg'd spark couldn't understand why we were wiring in 6mm. In his own words, 'isn't lighting meant to be in 1.5?' After myself and another lad tried explaining he still didn't get it. We quoted ohms law, volt drop etc. He said he remembered doing the formulas but didn't know what they were for at the time. He was also constantly telling us how he did side jobs for people, probably about the same rate as this guy for a mains change. The public then get a warped perception of proper sparkies rates. They are destroying thier own industry, are too stupid and ignorant to care and the system is helping them. This is what its come to now.