It was a great stay! Billie and Max were very helpful and friendly, letting us leave our luggage at their office before check-in and after check-out, which was very practical. The flat was perfect, very central, spotlessly clean, in a quiet neighbourhood. Definitely recommend to anyone! The only downside: if you have some mobility problems book a flat on the lower floors since there are quite a few stairs and no lift.
Looking forward to coming back to London and staying at one of the flats again!