Read the fine print about the building renovations; it is a work-site with few occupied apartments, exposed wiring, external dust and noise. Heating is reduced as is hot water and one morning, no water at all.
The up side is that Nick (and Mo) seem very nice, running their rental business efficiently with clean facilities, communicating well, and the flat offering all you need (if tiny) in this central London location. I'm sure things will pick up for them in a year or two once the building is completed.
For the visitor, think about whether a rent reduction is worth it for the strangeness of the experience.