I usually add glass between the wood and vanity. You can add a layer of stone or marble if you wish

I agree you probably need to centre the vanity and the cabinet on the wall or they could look a bit odd! You don't say why you don't want a space between the window and the vanity - just my opinion, but I would think 300mm could be quite useful for a bin, a clothes basket or box, or a small stool for putting clothes on? The only alternative to leaving a space, is to fill it with something as the response above suggested. To avoid it interfering with the window, you could make this something lower, so it sits level with the top of the vanity. This could be built in and the wall lining put over it to create a single "shelf" level with the underside of the vanity top, or if you can find some freestanding open shelving of the correct width, which could also be cut to the correct height, you could wedge that between the wall and the vanity side when fitting the vanity. Just bear in mind also, that you'll lose some of your towel hanging space if you put something too high in the space.

Thankyou very much!

Hi - about to renovate our bathroom and so far we are keen on using a combo of large marble/carrara floor tiles which will also go into shower area and up the walls of the walk in shower. We also want to use white subway tiles on another wall. For the vanity we are thinking of black wooden drawers with plain white stone top and white basin . For the tap ware we are keen on gunmetal but worried it might look dated in a few years. We want a contemporary look though. What are your thoughts on this combo. We thought of doing the vanity drawers in pale grey but think it might need the black to “lift” it as there is already too much grey/white in the tiles. Thoughts? Anyone got pictures of similar combos? Thanks!