Max and Billie's flat is in a great location, two mins walk onto the central line, westfields two stops one way and central London a couple of stops in the other direction.
The flat itself is easy to fine and once you get your head around the app the lock system is easy and you'll lose the headache of not carrying keys....However if you're slightly taller (i'm 6'2) bewear of the low ceiling when trying to get to sleep as you'll be ducking around alot.
Overall a great stay and would book again. For those driving down there is parking on street but it's only for 4 hours max at the cost of £16 so you maybe better parking in westfields for your duration as it's £14 for more than 14 hours onwards :)