Will’s place was great. We had three adults and three kids (7 years old and younger).
Having two bedrooms and two bathrooms was perfect!
The location is about a 10 minute walk to a tube station (Pimlico or St. James Park Station). Our kids were fine walking, but keep it in mind if you have small kids. There are great shops, pubs, restaurants, coffee shops, and more very close by. We ended up loving the location, despite a longer walk to the tube than we have had with other places.

The building is super secure, with two locked gates to enter the courtyard, and a secured building. The neighborhood also felt super safe. We often cane back late at night and had no concern.
One thing to note: While it says it can accommodate up to 6 people, I was say no more than 4 adults. The couch bed was fine for light weight small kids, but not for adults.
I would recommend Will’s place for your London stay!