I've just spoken to Tesla.
I was advised that a car has not been allocated, and if I see a car on 'Available Inventory' that I would like in different colour/interior then I should call them.
So I asked, does that mean I won't be allocated a Q3 car, answer was: if someone doesn't take their car then maybe it'll match your order.
I also asked if my colour selection was less common, MSM/White, they would not answer, but did confirm that most vehicles were already matched and allocated, and I should wait until 5th/6th September before calling back