Tile beading around recess

[Bodgedbuild]

I am in the process of re-fitting my downstairs loo following an extension and renovation. I have chosen tiles and I cannot use border tiles across the top of the tiles because the door only just fits past 6mm tiles so anything protruding would catch. The obvious choice is to run a quarter round beading strip all around but my problem is my sink is to be fitted into an obsolete window reveal (it now backs onto another room).
My problem with beading is that the reveal is to be tiled fully but the walls on the loo are only tiled 1/3rd the way up the reveal so I can't do a 3 way mitre like I would if just tiling around a corner. This means that I will either have to frame the reveal so that I don't have an odd step or do something different with regards beading.
Any ideas would be greatly appreciated.

 

[plastic_peanut]

I’m not sure if this helps but I have read your post several times and looked at the pictures and I still have no idea what’s needed.
Doors, windows, sinks?!?? Maybe a drawing or photo including all the challenges?

It could be me, it’s been a long week