The Party Superstore was/is my absolute favourite London shop until it was bizarrely attacked and gutted during the summer London riots. They have been since adopted as a concession by the local Debenhams but you can still savour the full delights of the products and nonsense on line.
The best magazine store in London! MagCulture stocks around 600 independent magazines from all over the world. They always have the latest issue of everything and you will ALWAYS find something you've never heard of before. Make sure you visit on PAY-DAY, as there is a good chance you'll walk away with a delicious new publication.