For a really special meal try the Bateaux floating resturant. My wife booked this for my birthday. The food is fantastic, ever changing scenery as you float up and down the Thames. After dinner they have dancing to a live band on board.
I too agree with Kevin (30/10/03) - Pizza Express next to Globe is great ! - Not only is the food reasonably priced, but the views are wonderful and the staff always very friendly.
Unsure where you are staying, but I can recommend Room 212 in County Hall (Travel Inn). The river view from this room is wonderful and in August there were lovely blue lights in the trees, in front of the hotel window. I like to get a few olives & cheese from Borough Market to have with a glass of wine, with the window open (summer months!!?!) to savour the view & reflect, before going out ! -
For a more expensive meal, I can also recommend People's Palace.