We had a great time at Mary's house - it is a hidden, quiet gem in the middle of London!
There were 6 of us (3 children, 3 adults) and it was a bit tight (everyone had to share a double bed), but for 4 or 5 people, it is a very spacious property, particularly for London standards. The top floor is beautiful: full of light and space for the master bedroom, with connecting bathroom (which can't be fully closed, but it's private enough) and a working space - I had to work all week and the internet connection was excellent. We were there in the middle of a heat wave in August, so it got quite warm but the fans made it manageable. In the first floor, there are two good rooms and a bathroom, and the ground floor is all kitchen + living room. The kitchen was well equipped - we cooked multiple meals and didn't miss much. The living space was comfortable and allowed for some great evening times.
The location is quite central and there's plenty of restaurants and supermarkets around. We were worried that the pub next door would be noisy at night but we didn't even notice it; London can be a noisy place (think sirens, traffic, ...) but this was a relatively quiet place. The street lighting is quite strong, though, which makes it hard to really have dark bedrooms at night (curtains help but leave gaps). We had a small issue with the first floor shower, which didn't get resolved during our stay, but communication with Mary and her team was active and helpful. We would be very happy to come back!