Brussels has three train stations, and if you're coming from London, you would probably get off at Brussel Zuid, which isn't the most interesting area. The Grand Place area, where most tourists congregate, is just down the hill from Centraal Station. A family member of mine stayed in a very nice hotel just across the street from the small church near Centraal Station, although the name of both the church and hotel escape me.
Many travelers will tell you that Brussels consists of the Grand Place, Mannekin Pis and not much else. I would counter that these people probably didn't explore beyond the Grand Place area. The city has all sorts of wonderful parks, museums, churches and Art Nouveau buildings, but it takes a little effort to discover them. If you have any interest in the world wars, check out the Royal Military Musuem. Half the building consists mainly of Belgian military equipment, but the other half has a huge collection of material from all sides in the world wars. Closer to the Grand Place, the Musical instrument museum and Royal Gallery are also worth a look if you have time.
Everyone knows about Mannekin Pis, but don't miss his sister, Janneke Pis. She sits in a dead-end street off of Rue Boucher. The cheeky look on her face is priceless.
Speaking of Rue Boucher, the food here is generally not that great. For some better seafood, head on over to Place Saint-Catherine.
And beer? I'll just give advice on what not to order- Jupiler, Stella Artois, Cristal, Maas. These are mostly standard light lagers. Go with virtually anything else!