This vast dungeon (well, it's in a basement) of a fancy dress store offers a stellar personal service. Staff will help you navigate some 35,000 costumes, from a sleek ant to a fuzzy Orvill duck, and then assist in piecing together a unique outfit for sale or hire.
Mad World is a great stop for period costumes, character fancy dress (they have everyone from Ron Burgandy to Rainbow's Bungle) and seasonal events such as halloween. Their get-ups are so on point that TV and movie production companies use them, too.
They also stock balloons and costume accessories, such as wigs, swords and more, and there's another Mad World store in Charing Cross.