There is a bunch of great places in London, which can be considered as the best not in the UK only but in the whole world. It's quite obvious that I'll begin my list with the classic one - 'Fabric' with a great heritage and especially rn after solving big conflict with the government.
Then, in no particular order: Corsica Studios, Village Underground, Shapes, XOYO, Phonox, Canavan's. Those are regulars but like for big events is Steelyard and Tobacco Docks.
London is famous for its club scene and it's a great place for electronic music.
I would recommend Phonox (personally my favorite), XOYO, Village Underground, Fabric. Fabric recently reopened and now has very strict security measures, making club entrance look more like an airport, but it's still worth a visit.
XOYO, The Nest, Phonox, The Printworks (opens Feb), fabric, Corsica Studios, LWE events at Tobacco Dock and Village Underground.
I'm surprised no one has mentioned Ministry of Sound - just five minute walk from Elephant and Castle.
Obviously Fabric, XOYO, Village Underground etc.