Some family members and I stayed at Joanna's apartment for a few days following a wedding in Leek. First, the location was absolutely perfect. It was quiet at night, and a very short walk to Portobello Road with quick access to both bus and tube. Joanna's apartment was lovely, with lots of character, beautiful art, and enough space for us to hang out in between outings.
The only thing that went wrong was we had trouble getting hot water consistently, but once I contacted Joanna she was very concerned and on top of it immediately. She was able to get someone to come over and fix it quickly. I do think that the five of us pushed the limits of the small bathroom though, so I would recommend that if you are traveling with a group who requires a lot of bathroom space and time, it may not be the best choice for you. I would also say (as the 5th person who had to sleep on the couch), that it didn't provide the best sleep, but the price was right and I knew what I was in for, so nothing against Joanna or her couch...but something to consider if you are thinking of booking for more than 4 people.
All in all, we really enjoyed our time in the Notting Hill area. We spent an entire day exploring the neighborhood and loved the mix of amazing shops, cafes, antiques, and art. Considering we had just a few short days in London, it was the perfect place to be.