May I suggest contacting the interior designer to request information on the tiles?

This is a question I face almost every time I talk with a customer when quoting a Bathroom renovation. You should always take to opportunity when renovating a bathroom to add ventilation into the design along with heating as in the form a underfloor heating of heat lights this healps with area's that would normally stay wet and reduce the problems of grout getting mould. As for selecting the right size tile this is really a personal choice there are lots and lots of options to pick from when selecting tiles. I always as what look are you going for? fine the look you like and study bathroom designs and take note of the size of tiles tou see in photos make a scrape book of idea's copy ideas pick the best bits. Small tiles can look great on a feature wall but to much of it can make a room fill closed in and to busy on the eye once you have added all your other fixtures and fittings to the mix. 300 x 600 tiles are the far most come tiles we lay where 600 x 600 are great for a modern look. 600 x 600 look great on a floor with 300 x 600 on the walls but I wouldnt suggest having three different tile sizes stick to the same or 2 different styles. it is a hard choice but go with what makes you feel comfortable and scrapbooking idea's is the best place to start. best of luck

To what extent do you plan to tile the walls? Floor to ceiling or just the wet areas (shower/bath section and vanity splash back?). I would personally find full walls in that tile over-powering eg. https://www.houzz.com.au/photos/regents-park-contemporary-bathroom-london-phvw-vp~31719695  I prefer a more restrained use like this where the floor tile is used on one wall to give the illusion of more depth with other walls simple and white https://www.houzz.com.au/photos/wet-room-shower-bathroom-hampshire-phvw-vp~23525132  (Not a professional of any kind but...) Looking at your layout, I would be inclined to go with the feature tile on the floor, the bath hob (sides and surround) and on the long wall running parallel with the bath. The other walls I would tile and/or paint white.

hi we have about six months ago now, re done our bath room , similar size to yours, and , i can take some photos and email them to you , we have maximised space, and walls , put in a white stone bath under the window , it is a metre in width , with a cool water spout coming off the centre under the window we pu t afalse ledge in to sit , candles etc on , , we tiles floor to ceiling, off white , wall mirror cabnit with three mirrors , inset into the wall so its only sits out a we bit from the wall tiles , floating bath room vanity , so that it makes the floor space look bigger , . matching stone square basin sits ontop of the vanity to one side so plenty of room to sit all your bath room stuff when need be , seperate shower all tiled as well , with inset , shelves for shampoo etc, also , when you open the bath room door and walk in when you close the bath room door behind it next to the shower is a very narrow floor to ceiling shelvec for towels, now the hole is there we jaust havent got the shelves put in yet. , we gt loads of comments as the bth room dosent look small evn though it is , , most expensive item the sqwat extra wide stone bath , made to order basin / tap ware and shower spray thing ,oh and the white stone vanity which we had made to order as well , due to the sizing .