Some delivery firms don't consider substantial parts of mainland Scotland to be "UK mainland". They charge extra. That has been the case for some business deliveries and even flower deliveries for a while.

There was a controversy about Perth in this regard a while back. I'm not even talking about Blairgowrie or Dunkeld or outlying places but someone trying to get deliveries to an industrial estate within the city of Perth itself.

The way things are going, maybe only the Central Belt will get preferential delivery fees.