The flat is advertised on Airbnb but rented via resify. It was clean and had a well equipped kitchen. It is located in a house with 18 floors, we were in the first one. There is a 24/7 concierge service at the door who gave us the keys upon check-in.
We had the problem that we needed three separate rooms for sleeping (we were 4 persons), the flat has two dorms and one normal couch in the living room. You cannot use this couch as a bed but there is the option to add another bedding for a fee.
Using the pools costs an extra 50 pounds. I assume that there is also a fee for the gym.
Nevertheless we had a good time in the flat.