ECP90

Hello, I am going to make a doorway between my bathroom and bedroom, making it ensuite. I've been watching a few videos and reading about how to do it. It seems doable even for a DIYER. This post is looking for any information people can share about making a doorway. Points I've noted down, standard UK doorways are 826mm wide. Anyone go bigger? Lintel above the doorway is extra 100mm either side of the door. Would anyone go bigger? What thickness would be acceptable? Above the wall where the doors going, there is only one beam across it. A builder had a look at it and said there no structural issues/its not supporting anything about it. Any thoughts/information would be much appreciated. Thanks.

Hello, I've pulled down my old ceiling, due to 100 years of cracking and fixing (it was old horse hair stuff). I'm looking to board my living room ceiling with my bedroom above it with 12.5mm plasterboard and to insulate it using rockwool for the soundproof mostly. Will 40mm screws be alright or should I use 50mm to take the extra weight of the insulation. Thanks in advance.