My early childhood was spent living in a van, small truck or bender. I know many people who live in a van today.
I see no issue at all with living in a small space. Particularly as a single adult, but I have known 5 person + families living happily in a traditional Romany wagon. Living with minimal goods can be a wonderful and freeing thing. In this case, there is also the ease of gas, electric, a loo and running water; I vividly remember my excitement the first time we had tap running water (previously pumps or wells).
However, while, for me, the lack of space is no issue at all, the price for that space (in the article) is bloody insane! One (small) room just shouldn't cost that much. Mad London pricing though, I guess.
My plan, once my children have left home, is to sell and either buy a studio or build a tiny home. Cheap to run, minimises fuel use, no clutter - fantastic.