I have had the pleasure of staying in Studio 3 (Basement), and also Studio 21 (Attic) on 2 separate occasions.
Studio 3 was very nicely renovated and modern. You could on occasion hear next door guests when they were going into their own Studio but nothing that’s not expected or overly loud. I could not hear any outside noise which was great.
Studio 21 was slightly different but was also nice to stay in too. As this is located on the very top floor, I was able to hear some outside noise but it wasn’t so loud that I couldn’t sleep and besides the mattress was very comfortable.
Overall, I would highly recommend. They accommodated my request for an early check-in, and also allowed me to store luggage at their nearby office premises on Kensington High Street. They are very quick at responding. They had a lovely little folder of hints and tips, and suggestions of what to eat nearby. Notting Hill Gate tube station is also very close - approx 3 mins walk via Exit 4. I’d be more than happy to stay here again.