Advice on electrics testing

Hi, basically about 5 years ago we had a problem with our house electrical supply, mainly the 'tails' were replaced. The national grid person warned us that we should replace the board so that we dont get caught out with the meter connection charge (or something similar to that effect). I worked for a car company at the time so asked the electrical contractor there to come and do the work. Showed up that night, and advised us to rewire. Long story short, he put a new board in and later he returned and rewired the house. Awkwardly, we were having an extension done at the same time. Long story short, two electricians doing 2 parts of the house.

The man who did the board, asked if the other bloke could do the testing. Seemed all above board.

Building control came, witnessed everything. Testing signed off.

BUT, turns out he just completed the additional circuits testing for extension. NOT the whole board and house circuits.

I want to understand how to proceed, this made me realise because we rushed the board replacement, we didnt put building control notification to replace the board.

Overall, is it best to submit a notification and get an electrician to come sign off the whole board? Both the original people are off scene. And would a different electrician happily do such a thing? What does it include?

TLDR: no building control or test and inspect in place.