Hi Tom, similar to Michele and Stephanie, I’d suggest contacting Principia. I recently gutted and refitted both bathrooms and all they asked for was the dates that the works would be taking place. I then had to fill out a form that Andy/Laurence shared with me, and my contractor had to sign it to – essentially outlining that the contractors would abide by certain housekeeping rules (music, noisy works etc.)
The plumber did a fantastic job of saving some space with certain pipes; others were unable to be put into the wall and a small box/beam had to be built to cover them up.
Happy to show you some of the specifics of what he did when I am back in town w/c 23 Sep onwards.