This is a very nice option if you're looking to stay in the Belsize/Hampstead region. The house is really amazing, built in the late 1880s. The room is very private and comfortable. There is a little garden nearby if you want some solitude and the whole area is very quiet. Right next to Hamstead Heath and easy walking to Belsize Park. If you like walking, you can make it to Primrose Hill in maybe 30 minutes. Very highly recommended!
Do note the narrow circular staircase. That is the only way up, so not ideal for anyone with movement challenges or really big luggage. Otherwise an excellent option!