and it's decent on the ceiling too...!
all sound advice, aquapanel on the walls via dot and dab is a good barrier....I always use a load of sealant up the corners before tanking....and make sure the tanking goes a good way up the walls, using the fibreglass matting, not just the jollop.
You can get a good, solid floor, with no movement, and use very flexible two part adhesives and grout, but water is an insidious bugger and can get through most things eventually. There are some very nice stone-looking trays that fit as flush, or as proud as you want them to be. Them buggers are solid too!