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.
One of my favourite places to snoop around is the food market open on a Thursday, Friday and Saturday. It's always bustling with crowds so great for people watching. You can get the best of anything here which is why it's hard to resist spending a small fortune.
I am definitely not precious about the materials I use to make my work, but every so often I find myself in need of something more specialised. L.Cornelissen & Son is a beautiful and well stocked art supply shop with extremely knowledgable staff.
The walk along the South Bank from Westminster to Tower Bridge will take you past a plethora or interesting sights and cultural hotspots. There's always something interesting going on too.