Hass's place is all what you need for your city trip in London. Transports (bus, underground, train) are just nextdoor ! the neighborhood is full of multicultural life, shops, supermarkets, pubs, restaurants and also parks (if you need to make some push-ups).
The place itself is very clean, and well organized for a small place. It can by noisy with the train crossing nearby but if you are used to big-city life, it's ok.
Hass is responsive by mail and there is always someone to help you if you need at David's Deli just below the room.
We have been there with my wife and two children and we don't regret it !