I stayed at the Sheraton Belgravia a couple of weeks ago and thoroughly enjoyed it. As a Gold member (Plutonium soon!) I didn't get an upgrade, especially as I received the last available room in the hotel, room 101. But it was a very nice room in a hotel with excellent service. As I was seated for the check-in, they brought me a complimentary drink.

Belgravia is my favorite neighborhood in London and I sometimes stay at the Carleton Towers or the Lowndes. Try the Nags Head nearby as one of the only privately owned pubs in the city.