An ATO is a “Approved Training Organization”. And you will need an ATO in order to recieve training for the issue or renewal of an instrument rating.
Not all flight schools offer the CB-IR/BIR theory, but here are a few.
Norway
Flygeteori.no – Oslo – http://flygeteori.no
Sweden
South Sweden Flight Academy – Malmö/Sturup – https://www.southsweden.se/