Great flat for our family of 4. We enjoyed 5 days at Sara's place. She met us at check-in and showed us around. There are 4 flights of stairs to reach the flat - no lift.
We especially liked the location in the nice neighborhood of Notting Hill. Had an awesome bakery just a few minutes walk away for breakfast goodies. Very close to the Notting Hill Gate tube station so getting around London was quite easy.
The house is well-equipped with even a combo washer / dryer in the kitchen. There is no microwave though.
Overall, we enjoyed our stay very much.