Hotel was lovely, staff very helpful, food was excellent, location excellent as it's so close to the Bond Street Tube station and there are loads of restaurants around.
The only hiccup was that our twin room was not ready by 3pm check in time, so we were offered a double room which my friend and I took as we were hurrying to get ready for the matinee of Chicago. There was only 1 washcloth and 1 showercap, but the housekeeping staff rectified this once we mentioned it. The only other criticism I have is that there was no mirror in the room itself. The only mirror was in the bathroom, which is not ideal when 2 women are getting ready!
Four of us stayed in the hotel and we thoroughly enjoyed our stay. I would definitely stay at the Mandeville again.