We thoroughly enjoyed our time and London and Joanna's flat played a large part in our experience. The location was fantastic. We were right across the street from Kensington Gardens and Hyde Park. We had easy access to public transportation and there were lots of restaurants, pubs, and shops within walking distance from the Flat.
The flat itself was very nice. It was clean, modern and very comfortable and had all of the things we could need for a 4 day stay. Joanna left us a very detailed welcome guide that answered any questions we may have had in regards to the apartment as well as suggestions for things to do in the local neighborhood and London.
My one word of warning to people looking at this apartment is to keep in mind that the flat is on a street with a lot of hotels and hostels. As a result there are people on the street at all hours and the window in the flat was not the most sound proofed one I have ever come across. That said, the noise from the street was a minor inconvenience at most and would not prevent me from staying at Joanna's flat during future trips to London.
All in all I highly recommend Joanna's apartment!