What sort of moron slams on the brakes & goes slow when on a long A6 straight they see the flashing blues of an emergency services vehicle coming the OPPOSITE way?
Yes, this kind of moron in a Seat Ibiza.
The car wouldn't impact your journey whatsoever. They weren't overtaking anything. You literally didn't even need to slow down never mind slamming the brakes on.
You're a moron, stop flashing your lights at people and sitting an inch from their bumper when there's nowhere they can go.