If you can do door at one end of long wall I would have vanity opp door then toilet then walk in shower at end. Should get at least a 600 vanity in. Towel rail opp toilet. Note towel rail can’t be on slider cavity but if you can do a barn door on outside you can put timber in wall to support towel rail.

(by reinforcing the walls of the cavity sliders we found it possible to install grab and towel rails) but my suggestions for this bathroom includes bath, shower, vanity and toilet with a hinged door centrally located to create privacy and allow for extra towel rails and clothes hooks to be mounted on the back of the door

Please note that you cant tile anything other than a skirt tile onto a cavity slider. This is a common mistake many people make.

I have a very small bathroom (about to attempt a renovation) which already has a slider and the present shower (with tiles) is on that wall. That is how it was when we bought it 8 years ago, built 14 years ago

Judy, this does not meet code. If you tile over the cav slider it wont meet code!

we have tiled over a wall that encloses a cavity slider by adding an extra layer of reinforcing to the internal wall that also allows for installation of grab rails that double as towel rails..we chose a solid core door and extra heavy duty tracks and the door slides inside the tiled wall with very little sound but, to allow for the extra reinforcing panel, the wall is 125mm thick excluding the architraves

Well, it was built by a builder (albeit, he went bankrupt straight after he finished it) I am not the original owner, but I presume someone must have approved it before the first owner could move in?