We stayed at Emma's flat for almost a week and are immensely happy we got to find this place! The flat itself is brilliant, perfect for 3 people (for 4 it may be a bit too much), comfy beds, great big kitchen, amazing shower... The views from the windows are lovely, the flat is really peaceful and quiet. So, all really, really good about the flat.
Now, about location... WOW. This really is central London but "proper central London", no "tourist trap central London". You can WALK to tons of interesting places (East London, the Southbank, Bloomsbury, Islington) plus lots of buses around... we took the tube ONCE and this was to get from the airport. It really is an amazing neighbourhood, really recommend the surruondings of Smithfield Market.
Emma was not there to pick us up, but left perfectly clear instructions on how to get into the flat and we had no trouble at all. Maybe the only, tiny criticism to add is that there were too many of their stuff around and we had to move them around to be able to make place for ours, but it took us about 5min to do so... and still much nicer to stay in a "lived place" than at an empty, cold, hotel room.

Absolutely recommend this flat to stay at, and if it's booked up, go and explore this wonderful area of London.