I stayed for four nights and would rate it 3 stars. One star for the great location near the train and subway, and another star for King's Cross Studios 2, who helped me switch room.
I booked a large room, but it was in the basement. We could hear and feel the subway passing every few minutes, and we also heard people walking above us. The bathroom was broken, lacking temperature control, which made the living conditions very uncomfortable. I had a very bad first night.
Since the service hours are from 9:30 AM to 6:30 PM, I went to King's Cross Studios2 the next morning to request a room change. They kindly found me a small room on the fifth floor. We managed to carry our luggage up since there was no elevator. The new room was clean but quite small, and even in early October, it was hot, so we had to open the kitchen window at night to cool down.
They don't clean the rooms during your stay, and you can only exchange towels during business hours, which was very inconvenient for us. On the bright side, being on the top floor allowed us to sleep better at night.
In the end, we paid for a large room but ended up in a small one and lost a night's sleep. Overall, it was not a good experience.