Originally Posted by Wiggums
I have a suggestion - go to Le Meridien Piccadilly. Although it's not in the Knightsbridge area and it's right on Piccadilly in Mayfair, a few minutes walk from the Fortnum & Mason, towards Piccadilly Circus. It has by far the most amenities compared to all the hotels in London I've stayed - and I have seen several websites refer it as a five-star-plus hotel. One downside is that parking's very difficult in the area.
For the price (I generally pay <250 quid) in the area, this hotel is one of the best values going. Recent renovations (primarily to public areas) should now be complete.