Not the most exciting place inside, but a lovely rooftop area which not all that many people seem to know about, 2 mins walk from Old St station. If it’s packed then The Red Lion is just up the road.
By far the best bagels in London, they are open 24 hours and being just down the road from my flat a bit too local. It is run by a man called Mr Sammy, who doesn't muck about with portion size. It is well worth a visit especially for their smoked salmon and cream cheese speciality.
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.