The ANO has worldwide applicability to registrations and licences issued by a delegated authority (i.e. the CAA).
Where the rules as stated in the ANO differ from those of a supranational authority of which the UK is a signatory (e.g. JAA and ICAO), then those differences will have been filed with those authorities.
So if you have a CAA medical, then it is issued as compliant with JAR-FCL3 with UK differences.
I'm sure someone will correct if I've got any of that wrong
