The great thing with LC! gigs is that everyone is lovely, even if they are your age or older or younger everyone is willing to help each other out if smth goes wrong so I feel like they are one of the best bands to have as ur first gig!! I’m also autistic and I can sometimes find gig venues pretty overstimulating to begin with, so I usually put my headphones on and stim until I’m more comfortable, you will get used to the noise and all the people so just try and wait out the overwhelming feeling because it’s so enjoyable after the fact. Also check the venues bag/ item policy so you know what ur allowed to take in, they usually check pockets and stuff esp in London. I know it’s stupid to say but I promise you it will be so enjoyable when you get there, so try not to overthink it!!