You need to buy a bidet toilet seat. We have had a Conway BA 13 which was very expensive at $1600 or morr but in our next house bought a Quoss for $500 which does the trick. Great for my elderly mother who lives with us but now I love it too.

Get a tile cleaning product from Bunnings. Will ensure that the integrity of the tile is not compromised. However, by the look of the stains it seems as though something has been used that was too abrasive, too acidic or that had bleach in it. I do not recommend to keep any product on for an extended period of time. 5 mins max application!

Though I don't know for certain, I think the cotton/linen shades are removable. I wasn't able to determine this by my searches. This could easily be confirmed by making an enquiry to supplier before purchase. Alternatively, a handmade one could be made removable by making shade slightly larger than frame and making ties.

I have a separate guest toilet without windows using a ceiling extractor fan - not a problem. I also have internal cavity sliding doors to bathrooms and toilets and love how they give extra space and options regarding placement of items. Another location alternative for you may be between the cinema room and the kitchen, depending on what you had planned for that extra space in the kitchen. Two metres is a wide hallway, if that is what it is? Ours is 1.3 which is considered wide (as we need to accommodate a wheelchair which has to turn into doorways). An advantage of a very wide hallway is it gives room for extra furniture placement such as bookshelves, linen or other cupboards if needed. I don't see a linen cupboard or pantry cupboard in your plans. Something else to think about is future proofing - try to cover future possibilities with regard to function, as making structural or fittings changes later can be more expensive, and may come at a time when you can least afford it (e.g. injured, disabled, children, aging or other such people visiting your home). Lives change, sometimes over time, sometimes in an instant, and suddenly the doors are not wide enough (especially the toilet door!), or the walls are not strong enough for a weight-bearing rail, and a host of other things. We put 900cm doors as a minimum and it makes life a lot easier, including moving furniture in and out. Universal Design principles are worth a look. Sadly these considerations are currently considered special or optional, although there are moves to change that, so that builders and architects will consider these things as standard.