If you are thinking to tuck a chair under so that’s out of the way, I would perhaps go He length of a chair and just over, to give room to put things on the desk itself. I measured my standard minimal but comfy dining chair and that was 40cm excluding the backrest. So perhaps go 45cm wide? Also think about using a ‘leggy’ chair, just like in the photo so it doesn’t take much visual space.

On Aliexpress the diameter given is of the overall diameter, here is a deep tone chime set on their site; https://www.aliexpress.com/item/33inch-Hanging-Wind-Chime-Large-Deep-Tone-Resonant-Wind-Chimes-Church-Bell-Outdoor-Garden-Yard-Home/32975926622.html?spm=2114.search0104.3.29.4c3c26462ghPcr&ws_ab_test=searchweb0_0,searchweb201602_10_10065_10068_10547_319_10891_317_10548_10696_10084_453_454_10083_10618_10307_10820_10821_10301_10303_537_536_10902_10059_10884_10887_321_322_10103,searchweb201603_6,ppcSwitch_0amp;algo_expid=e37168ed-1610-4a32-ab42-8738116496b1-4&algo_pvid=e37168ed-1610-4a32-ab42-8738116496b1 Excuse the huge link.

Miriam Do you actually mean columns as in structural elements or do you mean decorative pilasters? The size of a column is dependant on the load it is carrying and if these are load bearing elements. I would consult an architect and an engineer. There are standard sizes but the choice is driven by the structural requirements. If they are pilasters. Then a starting point would be to talk to suppliers of the plaster replica's https://www.lassco.co.uk/a-pair-of-english-cast-plaster-pilasters or others. They should be able to give you some guidance on the choice and size modules. Hope this helps Best David

Obobble and Suzanne C, thanks for the comments. I think the idea of putting the shower and toilet along the right hand wall is a good idea. Do you think there would be room if I put the vanity unit parallel on the opposite left hand wall, rather than underneath the window? (Sorry I like the idea of having a mirror in front of me rather than the window obobble!) Also what do people think are comfortable dimensions for a spacious walk in shower? If I put the shower in the back right hand corner then I’m not tied so much by the width of the window I think as it won’t jut up next to it? Ie it could be wider that 76.5cm?