Psy-Fi

I haven't been back over there in years but I'll second all the recommendations that have already been posted.
The Garage, Electric Ballroom, and Camden Underworld were venues I used to go to and see various bands perform when I was in town. Not sure if they're still in business now, though. The Royal Albert Hall is worth a visit just for its iconic status alone.
The annual Notting Hill Carnival is a lot of fun if you like festive street parades and parties but I think it's been cancelled again this year due to COVID. Hopefully, it'll be on again next year.
IWM London (Imperial War Museum) is another museum that might be of interest. I once spent an entire day there (from opening to closing) and I still didn't have enough time to take it all in.
Tower Bridge (often confused with London Bridge) and The Tower of London are must-sees if you're in the area.

That's all I have to add at the moment.

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