hi tony_m,
I used the BAL (WP1 I think it's called?) memberane tanking system. Very straight forward and it's sealed the room perfectly. I sealed the whole floor, and where the shower area is, from the pics you can see I tanked all the way up the wall but in all honesty, I don't think it was necessary to go so high. The water can't go above the height of the shower head.
The underfloor ...



