Hi @Barry - hmmm good point I have no idea! This is something we should probably check! The bricks don't actually get wet as the shower curtain goes round the whole bath but could this still be an issue just from the moisture in the air?

In my experience you can get a plumber and tiler for £2000 if you are having everything in the same place and everything is simple and basic. Most people take up the old bathroom floor and have to replace the flooring, or removing the wall tiles damages the walls necessitating new plasterboard/ replastering- or they want the fittings in a different place, they want floor to ceiling tiling. They want porcelain tiles (much harder/ longer to cut than ceramic (although superior)), underfloor heating, new lights, boxing in of pipes, extra strengthening of walls for wall hung furniture, decorating and the list goes on. Expect the labour to go up to £6/7k for a full job. The tiles and suite can be cheap or expensive. (£700- £12K) In my opinion you spend the money on the best finish rather than the best product- a good fitter can make inexpensive product look great.

For a start I would glass over the window opening so it is sealed but openable. Then a plain frosted plastic film on the other side of the glass. Because of the shape etc you are not going to be able to have a glass screen. So I would move the shower rail nearer the window. Then have a triangular waterproof curtain made that can easily hook onto some eyelets on the angled ceiling. A ships chandler would probably be a good place to source these things. Or A smarter and possibly expensive idea, screw a thin mast like structure with a groove to the angled ceiling. Then as you would a sail have your curtain move up and down in the grove. Otherwise seal and drain the floor immediately where the excess water is spraying which is a pain. When I was trained as a furniture designer/maker in 1981 at The John Makepeace School for Craftsmen in Wood, we had amazing original roll top baths with Carrara marble bases in each bathroom. The bases had a drain in so any water splashing out of the bath fell onto the drained Carrara, not ideal in this situation. The amazing residential course was at Parnham House, Beaminster, Dorset which was built in 1522, it had great detail even in the bathrooms.

It looks like the panels are attached to the wall and then the shower tray butted up to that. To be water tight the shower needs to be against the wall and any tiles or wall panel needs to overhang the tray so water run off runs onto the tray and not into any gap between the two. I wonder if the panels are attached to battons which have degraded (possibly due to water) and that’s why there is flex. To avoid further speculation I think you need an expert to look at it but based on what I can see on these pics I imagine it will have to come out and be reinstalled properly.