@ProDave this is an interesting assumption, and an incredible amount of judgement for an open forum for people who are learning on this journey. The industry being filled full of people who do things differently, shoddily, and with poor advice based purely on their experience is the reason we, as homeowners, cannot trust the advice presented.
The conversion was already in place, there was an existing kitchen where we intend to replace this. The builder who was used has already been removed from the project and the plaster has been removed. We have sought the guidance of multiple damp specialists. My intention here was get some perspective around the different recommendations provided from all of these people.