Generally, the day goes as follows.
Engineer arrives at your house/business premises.
Wants to see ALL your H+S policy, public liability, complaints form, etc.....
Then wants to see your issued certificates to date.
He normally picks two, that he`d like to see, and you `phone customers to confirm they`re ok (I normally forewarn customers that I`m regularly assessed, "to check I`m doing my job properly").
If they aren`t in/ inconvenient, he`ll pick another.
Then he jumps in your motor, and you go to the jobs.
He`ll want to see you performing the tests, and getting approx the same readings you put on your cert.
He`ll ask a couple of questions (remember - he ISN`T trying to catch you out - he`s making sure YOU know what you`re talking about).
Most inspectors are practicing sparx - If you want to know something technical, they`ll usually help.
word to the wise - when he arrives, be prepared. Offer a cuppa, and be ready to discuss what work you`ve done recently, eyc.
(At the end of the day, it isn`t financially viable for them to fail you; unless you appear incompetent!)
Brush up your regs, and be prepared for a live version of 2381, 2382 and a bit of 2391 thrown in.
Don`t try to waffle or bluff!!!! If you don`t know the answer to a question, say so. Much better than appearing to be a pillock.