A small place to eat with great vegetarian/vegan food just off Camden High Street. This place does an amazing buffet at a great price, as well as serving reasonably priced tea and juices.
Appreciate the 'bar hidden away behind a bookcase' thing is pretty naff but the cocktails here are unreal (try the Hot and Cold), and it's inside Milroy's Soho, one of the most legendary spirits stores in the city
The Greenwich Observatory with its green laser beam can transfigure any night sky. If you decide to cross the Thames via the foot tunnel, make sure you look out for the green ray. You can be on one side of the meridian in a minute, and cross to the other side on the next, without even realising it.
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.