I like option 2. Make a big statement--obviously you love carrara marble so go for it! You won't regret it.

could you please check the dimensions as they don't look quite right. Will need the whole closet and bathroom as i'm pretty sure it's bigger than 10'1" x 6'3" ( is that just the closet?

Thank you both for replying. Yes that wall at the bottom can't really be moved as it contains the soil pipe for the toilets. The main bathroom doesn't need changing, the cupboard from the hall is the airing cupboard so that can't be moved either. But I do think maybe we make it a wet room with a nice walk shower without the bath. Not sure about walking straight into dressing room - we'd have to keep it exceptionally tidy or it would annoy me...

It seems like you need more space than you currently have. If it were my house I would be looking to make the landing at the top of the stairs bigger, extending under the eaves, investigating either velux or a dormer in the roof pitch over the garage. If you could gain an extra metre under the slope it would be great for a bath. And on my plan I have pinched some room from the bedroom too.