The wisest words I can give you are that you should call a halt to this work until you've learned more about the subject.
I'm not saying this to be superior, or to put you down, but you are missing basic and important knowledge, as shown by the fact that you considered putting a 45A MCB on the end of 6mm cable.
Yes, you asked if this was OK, but trying to learn the basics of cable choice, rating calculations, load calculations, protective device ratings, cable installation methods, circuit design etc etc etc by asking only the questions that occur to you is a very unstructured way to go about it.
What happens if you fail to ask an important question because you simply have no idea about a particular area, and have no idea that you have no idea?
There is also the fact to consider that the work you have done, and are suggesting doing should have been notified to LABC in advance...