Tile layout advice for beginner

[Leroy Brown]

Hi all. So I am trying to plan the layout of tiles for my bathroom. Figured out the horizontal lines but cannot figure out the vertical cuts. The window wall which has an off centre window I think I shall be ok putting a tile in the centre as the wall will only take 3 tiles. See image attached.

Now the 2nd wall which I cannot get my head around has a recess for a cupboard and a niche for a towel rail. Any advice on where to start would be magnificent.

Thank you.