OP
sparks1973
only thing they care about is money..lol...He will spend the first hour or so just getting a feel for your background and how you approach your work. Just make sure you have all your documentation to hand as he will have to record that it is all in order.
The other guys have pretty much covered what is expected, and most of what you will be asked is in the osg and the electricians guide to the building regs, so just keep reading them.
Of course it will be stressful (if it matters to you), but always double-check your answers if you are not sure by looking them up.
Oh, and make sure the CU has all 3 labels on it.