I’ve heard good things about iklektik but haven’t been yet myself, couple of other options could be DIY Space or Rye Wax. From what I understand Oto get way more event pitches than they’re able to reply to let alone make happen, so I suspect that might be ambitious.
Finding good venues for grassroots music in London is getting increasingly difficult, to be honest, and attracting an audience when there are a million other things going on isn’t much easier. Even the friends of mine who’ve run critically acclaimed and popular club nights have been a bit ground down by it recently.
That’s not to discourage you, it’s still perfectly possible to create cool events, it just means you need to have a bit more of a think about exactly what you want to achieve and how much time & money you want to invest upfront.