In the basement of the hotel is the Dickens Bar. I love their lunchtime curry buffet (weekdays only), and we also head along there for drinks in the evening from time to time.
Up on top of the hotel is the TOTTs restaurant, with views out over the harbour. That has a Sunday brunch with unlimited fizzy wine, so a good place to go with a bunch of friends on a lazy Sunday.
Hotel website: http://www.mandarinoriental.com/excelsior/