Trouble is, they're no longer public but are a private, listed entity nowadays but still retain the monopoly on international packages sent via other postal services...and boy, do the bast*rds exploit it....>30 EUR administrative fee. And you don't have a choice as competition can't play. Time for a letter to the European Commission I guess. Anyway, when shipping to Belgium anything's better than post.
You don't have the option to clear the items yourself thus avoiding the customs brokerage fee? In Finland this can be done online.