Hi there my son has autism and I remember how stressful it was when he was first diagnosed and navigating him through different situations, some people were understanding others not so.
It might be well if you haven't already to explain to your neighbours about his issues and that you are seeking help, if he can't speak yet he's probably feeling frustrated and uses noise to communicate his needs, that being said kids can't help being noisy.
Does he like music perhaps when the noise is ramping up too much try to distract him with some soothing music, classical or just instrumental music.
If he has any special interests, trains, technology etc tap into those things, enter his world, they might calm him down and give you some peace.
While you wait for diagnosis please reach out to a lovely Facebook group called ASD child in SW London (most of us are based in Wandsworth). it's a lovely group that is very supportive. Please PM me if you need any advice and definitely get advice from the Early Years team at Siward Road or West Hill.