One major thing to consider carefully in a new bathroom design is whether you want to install a greywater system.
Toilet Roll Holders
We have three single-sided or cantilever fixing toilet roll holders in our current house and this is what they look like now. This first one is our main bathroom. It is seriously leaning, to the point that the toilet roll will only just stay on it.
This is our current ensuite toilet roll holder. It isn't a lot better :-(
This is our current entrance hall toilet roll holder. All three started out perfectly level!
What we have learned from the above images is that gravity always wins. There are no single sided fixing toilet roll holders worth putting in you home!
If you are going to install a toilet roll holder that has the toilet roll slide on from one side, then you at least need one like this Ikea Grundtal model, that has a fixing bar that is double sided.
The alternative is one with a central fixing point, where gravity works to keep it level.