C1Power

Hello everyone. I recently installed a 5KW Inverter system at my house. I have done all the wiring and install myself and now i have asked an Electrician to come out and inspect the install and supply me with a COC. When he got there i immediately got the feeling like he was trying to rip me off and basically implied that my install was completely wrong and that to be compliant he would need to change a huge about. he then gave me a quote for about 8k to do all this work. considering that all the wiring is already in place, I thought that this was abit ridiculous as i have been quoted for a full solar system ( 15 KW) and the install costs on that were 12k. now this guy wants to charge me 8k just to change a couple things and give me a COC? can anyone give me advice on where to find what the laws or regulations are for the inverter install, for example. Do you have to fuse both positive and negative cables from the battery? Do you need a combiner box? etc... Thank you in advance