Can the 46cm gap/wall between bath and cupboard be removed? If so, move the bath up into that corner and then put the sink in the bottom right corner at the foot of the bath. Keep short heated towel rail below window and add another short one on the wall beside sink (at end of bath) - or add tall towel rail where sink is currently.

If this will be a well used bathroom then you should visit a bathroom showroom and look at the size of shower baths and vanity units- when you know what you want in there you may conclude that you want to reduce the back bedroom size and make the bathroom a little larger

Can you move the door on the side where the sink currently and place the sink adjacent with the toilet? Because by current layout the bathroom Will be cramped and if you open the door you Will look directly at the toilet The ideal layout usually to align them in one wall so it creates seamless pathway from the door that placed near the opposite wall If moving the door isnt possible then switch the placement of the current toilet and the sink (the toilet directed toward shower just to make sure it doesnt hinder opening up the current door)

I don’t know how Jonathan does it. He’s some kind of spacial genius.