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.
Think this may be the oldest music venue in London? If it isn't, it certainly feels like it. I love the fact that you can feel the musical history as soon as you walk into 100 Club. Given it's central positioning I'm sure a lot of people of holding their breaths that it continues to stick around