Louise, I had a friend who lived in Helmsdale, East Sutherland, which shares a regional postcode with the Orkney Isles. She had horror stories of telephone conversations with mail order companies who refused point-blank to believe she did not live on an offshore island......
And when postcodes were invented, most inhabitants of the Outer Hebrides found their insurance premiums shot up because they were living in a "high crime area" - sharing a code with Paisley. They had to be given their own code (HS) instead, thank goodness.