I enjoyed the atmosphere of the spa - felt like I was in Thailand, rather than central London. For me, the neck and back massage was too firm. I did have to ask therapist several times to be more gentle - I would talk to them at the start if you book this. I could hear staff talking in the neighbouring room. Overall I would describe as invigorating rather than relaxing.
It was a relaxing experience, very quiet and tranquil. The facilities were small, we had to share lockers and there was one toilet and one shower only.