Brilliant solution! It really looks great. What sort of costs are involved in using such large pieces of mirror cut to order? Does the weight pose a problem? Only asking as it looks so good, I am wondering how to use the idea also!

Absolutely agree with blueskies60 ! Remove the artwork/bench/plant that's on the left and replace then with either a bookshelf or a tall chest of drawers. Perhaps the plant can be repositioned into the corner on the floor where this troublesome niche is (there seems to be more than enough light there for a plant) and just place something calm and simple in the niche itself - perhaps a Japanese style scroll or pen and ink art work set off with a more rounded object sitting in the left corner of the niche; a gorgeous rock, a lovely candle, a calming statue... If you have (my preference) a chest of timber drawers on the left where the current art work is, you'll break up the symmetry, have more storage and have another surface upon which you can place a changing display of objects. This is the area that I would utilise for a mirror.

There's a lot of timber going on here with the floors and the door, I would avoid any more features in this room and add a narrow console as the previous owner did. Just think, you didn't notice the crevice when you viewed the property. A console is easy and inexpensive, it's also functional if you use it for keys etc. Sitting a large plant (or cut flowers if you can manage the upkeep) on the console will add some vibrant colour and the mirror will reflect it adding depth. A few other accessories will help to dress it up. Consider baskets under the console or something similar to hide the crevice and cover the vast mirror. Whatever you decide to do, I'd love to see an after photo!

To assist with harnessing the sea breeze suggest a beautiful long narrow feature window that follows either side of the pitch of the roof (which will let in a lovely sky view plus breeze), or just have the top triangle as a window. Understand the desire to have the small window there however in a room with big glass/window features, the small window looks like an after thought and is at the wrong scale.