Can't say that places like Skyriver, Federal and Green Elephant fit your bill - clean enough but not places to hang around for longer than the main attraction .
Typical Line up and interior -
External Link/Members Only - quite big places with clinical bright lights and tiles.
At Green Elephant you get shown to a seat in a box room then the entire line up crams in at once which is epic but personally I've found Beach Club FLs back in my hotel best.
Maybe there are pricier, more upmarket spas offering what you want - if you find anything please report back!