We had a lovely stay at Seb's apartment. Seb and Nena are wonderful hosts, they're very accommodating and responsive, and were exceptionally helpful throughout the trip. I would rate their communication 10/10. The apartment is well equipped and is not too far from public transport. If you're looking to be in Notting Hill, do consider their Airbnb!
I will add the caveat that if you are traveling with older folks or people with back problems, some of the furniture may not be very comfortable or ergonomical. My parents (both 60 years old) were traveling with me and they experienced some back-related discomfort with the sofas, which they found to be too wide and deep, and the dining table bench, which has no back support. These are fine for people without back pain, but perhaps not very ergonomic for those who already have back pain.
Also, it's worth noting that this is a lived-in apartment which is full of the owner's actual belongings, and therefore it can come across as a bit cluttered. It's perfectly fine and clean by most standards, it's just that you shouldn't go in expecting an Airbnb that looks professionally cleaned and entirely unoccupied.
Other than that, we had a good stay! Thanks again!