Literally, if you're a slim/average and attractive young or middle aged woman, you've got nothing to worry about, especially if you are hot.
As a white guy I've been to a few of these places with ex girlfriends. I had no threatening looks towards me, maybe because the black guys just wanted to be inside her. But I'd never go to them as a single white guy, not a chance.
Single white women, literally, get in there, live it up, zero worries.
By the way, black clubs/bars I mention were in Dudley and Birmingham, England UK. I've no experience of London.