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.
NOTE: Not all ATOs offer the CB-IR/BIR theory, but these do:
Oslo Flight Academy – https://www.osloflightacademy.no
eFlight training – Trollhättan – www.eflight.se
South Sweden Flight Academy – Malmö/Sturup – https://www.southsweden.se/