The flat is a compact studio, well suited to a single traveler or a couple. Holly is an ideal host, there when you need her but leaving you to manage independently otherwise. She thinks of everything for a satisfying stay: a comfortable bed, well supplied kitchen, useful neighborhood recommendations, even a fully charged cellphone for local calls while exploring London. The studio is in one of London's most livable (and visitable) neighborhoods, with some of the world's best museums a short walk away. The studio is equidistant from two Tube stations and has a great array of shops and restaurants within an easily walkable radius. Perhaps most important of all, the room is wonderfully clean and well maintained with excellent plumbing and heating. And it is amazingly quiet for being in the middle of such a buzzing city. There is access to a large garden/park in back of the block of apartments; it looked lovely, but a wet December was not the time to enjoy it.
The one downside is quite literally that: the room is below street level, so it never gets very bright in the room. Of course, if you're doing London properly, you shouldn't spend a whole lot of time in the room anyway.
A fine choice for a stay in London.