The old shower tray was holding moisture and allowing water to penetrate into the fibre sheet. As you can see this it really needed replacing. Once the room was decontaminated the plumbing was updated with new copper pipes,wastes etc. The framing was done for the features and services. Electrical was also done before sheeting.

Tip. When sheeting always mark on the sheet where the services are so that you dont put a nail into them by accident.