Shower has leaked and caused the floor to gone rotten at the edge of and underneath the shower tray so it will need to be removed to see how bad damage is and repair the floor.
Plumber/ bathroom fitter came round today to look at it and basically said that it would not be advisable to reuse the tray or surround as it wouldn't be possible to guarantee a good seal. Then went on to say that the floor to ceiling tiles would also also have to be removed to check the wall not damaged - effectively I'd have to have the whole shower room redone.
Another builder seems willing to go down a less disruptive route of refitting the old shower tray and enclosure and no mention of taking all the tiles down. The shower is not that old and certainly would not be replacing it if the leak hadn't happened.
So who is right?