Motorbiking might have been talking nonsense. There are seven food outlets available to all, and just three available to non-Schengen citizens. And one of the non-Schengen food outlets only serves pies, hot dogs and finger food.
As UK was not in the Schengen zone before Brexit. Brexit has had no effect on UK passengers using the non-Schengen food outlets.
In addition, international travellers face longer queues, for processing through the airport, than domestic passengers. Schengen passengers are considered domestic travellers.
Kos Airport Hippocrates is the airport serving the island of Kos. The airport is located near the village of Antimachia
www.greece-airports.com