Hello.
I hired a builder, the cost of the build included everything including electrics. The building work was fine but I was not happy with the electrics, i.e missing grommets, no sleeving on earths, no earth to back box etc. The builder was not an electrician but said his mate was and would sign it off. That never happened. I fixed the issues, as I have some experience from what my father showed me. I called in an electrician I had used before and trusted to sign it off for BC. He came to see, said the electrics were fine, I was correct to sort earthing etc out but only issue as could not sign it off as since Jan 2016 Metal CU was required. So this is full story. I like the electrician, I did not want to make it sound like he did work and then trying to get extra bucks at end. Builder was paid to do job and failed. BC wont sign off without Cert, so I had to call in the only electrician I have ever used. I assume though all this makes no difference as a Metal Box is not required.
I think the initial ÂŁ125 for inspect/test sign off was fair. It was only the box I am CU I am questioning.
Hope this helps.