I hera you. 6ft is rather narrow. :-)
AFAIK, our building codes don't allow rooms a small as that (apart from bathrooms.) A 6ft x something "room" would be designated a "walk-in closet", which is pretty much what a box room is, right? -- The smallest bedrooms I've ever seen on a house plan were 9ft x 8ft. But I've never seen one in real life. 10ft x 8ft are fairly common in older homes. Current homes have 10ft x 9ft and larger. Since the 1950s, new houses all have built-in closets (wardrobes) in bedrooms. They increase usable space but create access problems, of course.
I now recall the model cottages put up by the GWR at Swindon. One of them is kept in original condition as a museum pieces. Bedrooms barely big enough to hold a narrow double bed with about 1ft on either side of it. Stairs about 2ft wide. The whole floorplan about the size of a living room in a modern (Canadian) house. "Cramped" would be a polite description. There is evidently an ancient tradition of broom closets masquerading as bedrooms. :-)
Our house plan showed three bedrooms and one bathroom on the second floor (first floor to you.) We redrafted it before construction to give us two bedrooms, 1/-1/2 baths, and a walk-in closet. Much nicer.
HTH