A friend of mine and I stayed at John's house for five nights and we couldn't have asked for a better experience!
The house is located in a nice quiet area and it's beautifully renovated and everything is very new and clean. The room itself is very clean and cosy, with a large window overlooking a park and the bed is very comfortable with a good mattress. The room is located on the top floor, with its own private bathroom and since no one else lives on that floor, it's very nice and private. The bathroom has a nice shower with glass doors and good water pressure and it's, once again, very new and clean!
John also has a big, well-equipped kitchen that his guests can use as well, including his espresso-machine and toaster and such. John himself is a very nice and helpful host. He picked us up from the underground station with his car and had fresh towels and watter bottles and even some breakfast things waiting for us when we arrived. Since he works most of the day, we didn't really see a lot of him, but he was always open for a nice chat and giving us tips on what to do and how to get around in London.
The house is very well connected as well. With the bus, which is just a minute's walk from the house, you'll be in Camden Town in about 10-15 min and in Trafalgar Square in about 30-40 min (depending on traffic) and with the tube, it's even faster and very well-connected. We had absolutely no problem getting around.
Overall, a great experience, 100 % recommended!