in my opinion i would use ladder if under 9 metres high but would ensure it is footed and rubber ladder mits on the top, if over 9 metres then i would use a zip up scaffold others have mentioned a small cherrypicker but be aware these are heavier than they look and the floor may not be adequate to take the weight, even if the floor can take the weight any tiles that have been laid and have airpockets in the tile adhesive will crack unless you board the area out to run the machine on, finally some mention dragonfly or similar these are fine for maintenance cleans but even then they do not clean the sills so so personally dont think they are much use, when you do a method statement put the reasons you are using the method of access chosen at least then it will show you had assessed the situation