My husband, 7YO, and I just got back from our 2-night stay at Billie and Max's studio.
Pros - Location (walking distance to Kensington High Street, Hyde Park, Tube, grocery stores, cute cafes, Dishoom); Cleanliness (studio was spotless and they open the futon for us); Communication (we got in very early in the AM and were able to keep our bags in their office until the studio was ready. Billie/Max's team was very kind and polite when we dropped off bags); Technology (keyless entry with an app on your phone).
Cons - Size (It's a studio so we expected it to be small. It was fine for the 3 of us for 2 nights but it's not ideal if you need a lot of space); Kitchen (the studio had a hot plate, small dorm-size fridge, electric kettle, and the basics but it's not somewhere you can cook an elaborate meal. We weren't planning on eating in so we just used the kettle for tea and the fridge for water/fruit).
Thanks Billie and Max!