Have you gor any ventilation in your wet room? Leave the door/window open as much as possible, that helps,there's another topic on this subject somewhere, have a look through the pages.Morrisons Anti-Fungal/Mould was supposed to be a good one to use but if you've tried all the top brands it probably wouldn't work.Someone else might have a better answer.
I used Mould remover bought from Woolies and it is fantastic. It is the only thing that works for us. You have to leave it on and go a vaccum or something and come back and rinse. It's that easy. But the smell is pretty toxic until you rinse, so open a window or something.