The two hotels I'd recommend are The Gore and The Radisson Edwardian Vanderbilt, both in South Ken. The Gore
is a wonderful little hotel, very English, with a nice library/reading room, restaurant, and bar. It's right down the street from the Albert Memorial. ~150GBP in the fall.
The Vanderbilt is somewhat cheaper but still nice. As a chain, it has less character than the Gore, but it's not oppressively businesslike. It's actual one of the least "chainy" of the big hotel franchises I've seen. Decent bar, nice, spacious rooms. The location, though, is what really makes it a good deal. The Gloucester Road station is literally across the street, and Racine, Harrods, and the V&A are all within easy walking distance. What's really nice is that the hotel's just the right distance from the Knightsbridge Patisserie Valerie, so that you have a brisk walk to awaken you and hone the appetite before breakfast.
Do a search for shopping info.