Hi Vicki, I would go for bigger tiles, ones that are 60 cm x 30 cm. If you use smaller tiles the outcome may look too busy with your chosen floor tiles. I also suggest choosing very light grey wall tiles, the colour of which matches to the grey background colour of the floor tiles. That would give you the industrial sort of vibe you are aiming to achive. Order different samples and see how the combinations look in your bathroom. The colours can change dramatically depending on the lighting. Kati

A friend had panels installed. Not sure of the brand. They are great in terms of cleaning. No grout means no mould. Just a squeegee to clean everything. Downside is they are plastic so can be dented and even cut by a screwdriver or drill while the accessories are being attached, but should be fine under normal use. You cannot use harsh abrasives and chemicals should be tested on a spare piece of panel before using on the shower.

Niches are usually built into a second wall so it may well be too late but the window idea is good. You could put a basket on the windowsill and put all the toiletries in it.

Your problem is leaks over time when the grout and adhesive shift around. If the levels are as off as they look, you need to apply waterproof plasterboard prior to doing the tiling. Sorry but you are better to do that before going further.