I called Tesla UK yesterday to change my order from white paint to blue paint and they said changing my order would push the delivery date from September to November. While the UK website has not changed yet I think this is an indicator that the cars coming to the UK will have the new battery - otherwise, they'd continue to deliver them throughout September and October? I think there must have been a factory shutdown to accommodate the Q3 changeover from the old batteries to the new, and they're getting rid of the last of the old batteries with the deliveries this month.
Wishful thinking maybe, but with an entire month missing of deliveries it does make sense for a factory shutdown due to battery changeover is the reason. I won't know for sure until they update the website to show 580 miles (614 km).