This is one of my favourite places in the whole of London.
Cernamic, run by Nam and Susi, they offer some fantastic workshops and at a very affordable price. They have really cultivated a welcoming environment, full of lovely people and a place to share and recieve knowledge.
Just above the Dorfman Theatre lobby at the National Theatre, is the entrance to the high-level walkway, a public walkway that overlooks the National Theatre props and scenic workshop.
It's free and is a unique chance to get a glimpse of what happens backstage. I love popping in when I'm on the south bank, as you get a completely different sight each time, depending on which production the workshops are working on at the time.