I am a member of Spa London and I am profoundly disappointed of the Ironmonger row spa.
Firstly and most importantly, the spa is a threat to your health as the room with mint steam has a good deal of damp on the ceiling. Even if inhaling damp and having damp in wet warm areas is extremely harmful for one's health, the administration still keeps the room open to clients.
In the evenings there is little to no aromatherapy oils (or at least smell) in the steam rooms. Tea, apples and shower gel are almost never available in the evening. Whenever I called to book, the phone was rarely answered. Left voice mails and on one occasion I wasn't able to use the spa as no one had recorded my booking left on the answering machine.
On top of that, when I signed up I was told that I can use the membership in other Spa's but found out that I can't.
Would advise other users to look for other places.