I hope someone can help you, Diamonds. It won't be me, unfortunately.
See this story and the price quoted kind of freaks me out. A week ago I finally chiselled off the bottom row of large tiles on the wall of tiles along the bath as they had started bulging and I thought get them off, scrape away bits, reapply cement and jobs done. But I got delayed between taking the tiles off, which to be fair I did on a bit of a sudden whim, and the getting of the cement. So in order for us to be able to have showers I made a waterproof cover over the blank part of wall, heavy see-through plastic held in place with polytunnel repair tape and an extra layer of gorilla tape. So far, so good.
Then I noticed after a few days that in spite of my great and working waterproof barrier that the plaster behind was displaying water marks whenever the shower was used. Oh Nooooooo! That means there's a freaking leak somewhere in the plumbing up to the shower inlet.

Would mean taking off a whole 2 walls of tiles and that would just be the start of my troubles.
I've spent a few days looking and thinking and I simply cannot afford this disaster. So my plan is to wodge on a load of cement and stick the feckers back on and hope they hold up until things improve with my economy.
Why did I have to poke at this problem in the first place?

Ignorance was bliss
I hope your bathroom karma is immeasurably better than mine.