The information is available on the FCL website, in the Policy Update of 30/01/2001.
IR(A) or (H)
An applicant holding a PPL or CPL who meets the experience requirements
of JAR-FCL 1.190/2.190 shall undergo a full approved training course for
issue of the instrument rating as required by JAR-FCL Subpart E,
irrespective of whether the ICAO licence held included an IR granted by
the state of licence issue.