Sheer Bliss is fairly modest in appearance, it doesn't LOOK like a top spa but I can assure you that the treatment, quality of products used and professionalism of the staff is excellent.
I discovered it's a family run operation and they genuinely care about the level of service - unlike so many top spas in London which seem to be franchises or within hotels.
I was really surprised by the whole experience, I was expecting a cheap and cheerful facial and massage and cannot rave or rate this more highly.