how about continue boxing all the way to the window and use it to house concealed shower pipes and taps also. adding a niche for shampoo and soaps / candles. to have a mirror cabinets above the sink and toilet and under sink cabinet. also fill the gap on the other side of the bath adding a cabinet for laundry / cleaning stuff.

I can’t see any images but it might be my internet connection as I’m in the middle of the North Sea on route to Norway. At home my vanity unit was bespoke made with a drawer pack each side and 2 full height doors under the basin in the middle. Worktop was sourced by us and then loo was purchased separately. Ask a local carpenter to do it. Easy job.

Hi, It's hard to tell without seeing photos of the tile & vanity unit colours. If you're going for a tonal bathroom look, a vanity unit in a colour close to the wall tiles will stand out the least and create a soothing look. I think you are right in thinking a dark grey unit will be too strong given the presence of anthracite on the window & towel radiator. Would you consider a wood effect vanity unit? They pair beautifully with grey and give the look warmth.

Obviously a wall hung unit would show more of the floor so would give the illusion of more space but a floor standing unit would conceal the boxed in pipes, the sink pipes and would give you more storage. A bathroom fitter would be able to fit the unit neatly up against the box. But you would need to choose a unit that can be modified easily.