I had a very nice experience staying a Nielsen's place. The apartment is lovely, very nice decorated and the views are mesmerising. Nielsen was very nice and helped me out with all my questions about London and suggested me new places to visit. Same did Angela, his wife.
I recommend staying at Nielsen's apartment, it has a very good location and they are both very nice people. I enjoyed the conversations and when we watched the fireworks for the Guy Fawkes day, those were the best views!
The only reason I did not give 5 stars it's because they usually made noise in the mornings when leaving to work, and I personally have a very light sleep. But besides that was all good.