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.
The best way to practice for your exams will be by using aviationexam.com.
Not all ATOs offer the CB-IR/BIR theory, but these do:
Norway
Oslo Flight Academy – https://www.osloflightacademy.no
Sweden
eFlight training – Trollhättan – www.eflight.se
South Sweden Flight Academy – Malmö/Sturup – https://www.southsweden.se/