A short walk from Oxford Circus tube station, Kaffeine is easily one of the best coffee houses in London. Whenever I'm working in the area I pop in beforehand to kick start my day with a well-made cappuccino.
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.
I grew up in Brighton which is full of cheesy bars like this. If you can handle being surrounded by multiple screens playing Kylie at full volume, its pretty much the cheapest bar in central london. The cliental is so varied its great for people watching and completely un pretentious.