Had my guest bathroom completely done, soon after I moved here. I have soft closures on both the loo in there and in my en-suite. I detest those that drop down with a bang. A good quality soft closing seat, properly fitted should not move at all.
I did not change out the loo or the wash basin, had those just re-fitted into their new positions. Needed a new bath, and shower over. As they had to fit a new false wall to cover the pipes over the bath, they also made a small alcove quite high up there to take shower and shampoo bottles, etc.
This is a totally internal bathroom, I had it done all in white with silver coloured, glittery accessories. It is really lovely, and bright and so very clean looking in there. Visitors always comment as to how nice in there when they use it.
I do agree regarding those seats fixed to walls in shower units. They always look grubby to me, (even when they are not). I purchased a fold up free-standing, shower stool when in my last house, this came with me and goes perfectly in my en-suite shower. It still leaves lots of room, but if someone else is using that shower, it is so quick and easy to fold up and remove. The one I have is backless, but you can get these with both back and arms if required.