What to do in London for a day in September

[BlumminKids]

I'm going to stay with my cousin in September - date tbc. She lives 40 mins outside London so we want to find something to fill a day. I'm not particularly into history but love arts, crafts, markets, shows etc. Don't mind a bit of shopping and love decent food.
Does anyone have any recommendations?

I recommend not going during the second week. There’s a tube strike, which means the buses will be absolutely packed.

If you like modern art, the newly-opened Moco museum ark Marble Arch is excellent. It’s also very close to Frameless which is a brilliant immersive art experience.