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Small bathroom renovation: re-line walls

I'm looking to renovate our small bathroom in our 1950's wooden house in Hataitai. The room is approximately 1.6mx1.8mx2.4m, has a bath with shower over it, handbasin & mirror, toilet, a window, a small cupboard and a door. Which are all pictured in the photos I've attached. We want to re-line the walls, keeping the plumbing as is, and, if it's a thing that can be done, use a single piece of plastic/acrylic in the wet corner of the bath/shower. There are a number of other things, including replacing the mirror, tiling lower side of the bath, and maybe replacing the toilet, that we would like to discuss with you.