The definitave document is JAR-FCL 1.190
An applicant for an IR(A) shall hold a PPL(A) including a night qualification or CPL(A) and shall have completed at least 50 hours cross country flight time as pilot-in-command in aeroplanes or helicopters of which at least 10 hours shall be in aeroplanes.
Any FTO offering these courses has to have a Training Manual that clearly states the course pre-entry requirements!