We were two friends and stayed two weeks in Anna's flat. We would definitely recommend it. Small and cosy, it looks exactly like the pictures.
There are two bedrooms. One room a little bigger with a double bed, and the child room where an adult can comfortably sleep during two weeks. Big kitchen, so great for whoever likes to cook. And a living room, with TV, dvd player, etc. and... THE terrasse! Fantastic in the summer! Clean. And Anna left us plenty of space for our staff.
It is very well situated. Very central. A little walk away from Baker Street, where you can catch several underground lines + buses, not far from Marylebone High Street (a great place with pubs, restaurants and shops). You can walk to Bond Street.
I felt safe in the area. And enjoyed very much this little cosy nest.
There is a Thai restaurant located right below the flat, and their kitchen ventilation arrives on the terrasse. So I was a little worried about that the first evening. But it actually didn't bother me anymore afterward.
Should I need to spend some weeks in London again, in the future, I would definitely check if Anna's flat would be free!