I stayed at the Melia to participate in an event of one of my clients. I arrived early, just before 12 noon, and there was no room available at first. This is unusual as some guests check out early in the morning so there should be some rooms ready at around 11. When I finally got a room (I had to change and wanted to shower), it was really small - smaller than you would expect it from the hotel category or the hotel website. Also, everything on the floor and in the room was very british old-fashioned with dark colours, wood, thick carpets etc. Not at all Melia style but that often happens when a cool hotel chain acquires hotels abroad and just puts its label on them.
The good thing with the (new) Spanish owners is the breakfast: It combines the best of several worlds, including Spain. This was really delightful. Also the location is really good: Almost on Regents Park, and just a ten minute walk to Oxford Street / Soho. The area is hugely preferred over the more touristic areas like Russell Sq or Picadilly C. Unfortunately, the bad rooms make it impossible to recommend Melia.