you can use it on plasterboard and plaster just prime the walls first with nicobond primer. the rep told me the unique would be ok in a domestic shower but not power showers
the no more ply is miles better than ply just dont get the glue on your hands. use the same trowel on all walls. i personally would use 8mm notched trowel. apply adhesive to walls instead of backs of tiles. the benfer tanking gear is quality as well
ultra slc will go up to 50mm in one go. check out the instarmac website for full spec. i would get the floor as level as possible before laying any covering.
9 out of 10 jobs i do are in brick pattern. everyone is having it like that but i think in a couple of years it will look dated. i personally like them laid landscape with opus pattern on the floor. thats 4 different sizes of tiles in a set pattern