This was not my mistake but I needed to fix the problem.
We bought this place to live in while we build the Belair house and although I knew there were a few loose tiles in the shower a bigger problem was waiting to be discovered.
When the original wall lining was nailed in place a nail had been driven into the pipe between the breaching piece and the shower head. The resulting leak caused all the timber stud work to rot away. This didn't happen straight away of course, the nail blocked the hole for a long time, until it eventually corroded away. The leak only happened while the shower was in use and any water found its way back into the shower so it was never detected by the previous owner.