Shower wall advice sort

I've a very old house (1700ish)that has been mucked about something rotten. An old hall way has been turned into a shower/toilet. But such a bad job was done (of the shower part) that the tiles keep coming off both an old original wall (hair & crumbly type plaster) and a newer plasterboard wall. It looks like the tile adhesive used is not waterproof! Except for the bits I've repaired, which I can't get off with out doing severe damage to either wall.
So I've removed the whole shower - wish I never started :-(
It is such a mess behind everything that I was thinking of using some sort of waterproof board (WBP?) then attaching the tiles to that. (BTW one FAQ says to use PVA another warns not to with waterproof board<?>)
Otherwise I have to get two walls, one old, one new, re-plastered.
An other choice is a ready built shower cabinet but they don't look as pretty. Or that wall-board stuff that is already waterproofed for bathrooms/showers.
Your advice would be much appreciated. Slatts
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.