Thanx for replies everyone, but question remains open:
Indeed, there are specific designated waypoints (as per AIP), over which AIREP reports shall be reported ("fireflybob" refered to them). But Annex 3 does not refer to these points, from the wording it uses, it is clear that AIREP shall be made once an hour together with position reports (if they are used), if acft is not ADS-capable.
Can anyone clarify this?