My family and I (7 people) stayed at Jon's place for a week at the beginning of January. It is a fantastic location. Being just a few blocks from Waterloo station made it really easy to get around the city.
The house is really well sized with proper bedrooms. The listing is accurate about sleeping arrangements. Nobody needs to sleep in the living room here. There are 4 bedrooms in all, 2 on the second floor each with an ensuite and double bed, and 2 on the ground floor with a double bed & sofa bed in one, and 2 single beds in the other.
The living area on the main floor is nice and large with lots of places for people to sit. The kitchen is large and has a reasonable stock of dishes and cookware.
When we arrived, I discovered a few maintenance issues. The toaster didn't work, a door handle was broken, and the extractor fan in the kitchen needed to be cleaned. However, Jon responded to my questions almost immediately and got the issues resolved.
I wouldn't hesitate to stay at Jon's place again the next time I'm in London.