We stayed at Sonia's flat for a week while visiting London. The space is fairly small, but it met or exceeded our expectations in every way!
The hosts were very flexible with us on check-in, were very helpful with tips, and were also prompt to respond to questions/requests.
The apartment is in Fulham, which isn't "central" to London, but we still found everything to be very accessible via bus/train. There is a bus stop right outside the flat, which can take you to the nearest underground station, and there are many shops and restaurants within a short walking distance. We loved waking up and walking to the nearby cafes for breakfast and coffee every morning! There is also a convenience store right across the street, where we were able to pick up snacks or essentials before/after a long day of sightseeing.
The only negative for the flat is the small/tight spiral staircase that leads from the main floor to the bedroom. It normally wouldn't have been an issue for us, but I had injured my foot while walking around, and it became a bit difficult to ascend/descend the stairs to the bedroom. It was also a bit tight trying to haul luggage up/down the stairs. Again, it's probably not an issue for most people, but I could see it being problematic for older travelers or people with disabilities.
Overall, we loved our stay, and we can't wait to go back to London!