The building should not matter, as long as it's got a roof, four walls and some good lecturers. I actually prefer the older buildings, which have a sense of history that you don't get with the new shiny glass-and-metal things they put up nowadays. The stone masonry, wooden floors, cast iron radiators, old libraries, fluorescent lighting, etc. give a sense that you're following in the footsteps of some of the great British mathematicians, rather than just googling their theorems on wikipedia in a computer room build from four pieces of glass. Ugh.