I stayed at Mark's place for my first month in London and I would highly recommend this place. The house is located in a beautiful neighbourhood and has great accessibility to 3 tube station, Kings street and Westfield mall (you can walk there).
Additionally Mark was a wonderful host (he literally lifted my heavy bags on my first day of arrival). You can have great conversations with him when he is around and in case of any queries/help, he is readily accessible.
Overall, it was a very comfortable stay. I would highly recommend this place in case you're for a place (short term or long stay) in London..