Helene's place was a fantastic find for us. We stayed for an entire month because of its central location--walking distance to King's Cross/St. Pancras Station--and it had everything we were looking for in terms of a long term-stay. The apartment is exactly as described; it's bright and beautifully decorated. I appreciated how quiet the apartment was even though it was located on a very busy street. This was important because we have a preschooler who still needed naps and so a quiet room. On this note, we also liked how the apartment was close to parks/playgrounds, and that it was located in a family friendly neighborhood with nice grocery stores (i.e. M&S, Tescos, and Salisbury), great restaurants, and a farmer's market within walking distance.
Helene answered all my questions beforehand, and was communicative throughout the entire trip. We would certainly stay there again and highly recommend her place to anyone looking for a great place to stay in central London.