A great place to start the day if you are in South London is Federation Coffee in Brixton Village. The food is great and so is the coffee. This is a very chilled place where you can get both and indoor and outdoor experience (even though the whole place is under the Village roof).
The most special and charming place to get art supplies and materials.
L. Cornelissen & Son shop is an artwork in itself and one of a kind. The staff are incredibly knowledgeable and kind and is always a delight to stop by.
I grew up in the countryside, and if you're ever in need some instant escape from the city, this place is like a time warp. It's a huge space full of over grown mausoleums and graves, feels like a movie set. They also do tours.
Being down on the underground can be quite stressful and draining, but if you have the chance to look up and into the details that has gone into the tiling of the platforms and stations you might start to see some beauty down there. A lot of stations has bespoke tiles and decorations, almost a century old.
Bethnal Green station is one of a handful in London to have been given a very specific additional decoration to the classic cream tiles and name strip. Easy to miss, but dotted around the station are a series of tiles with raised motifs on them, representing aspects of London and places that the Underground visited.
Or for typographers: check the type on Hampstead station or Holloway Road for some inspiration.