As you mentioned Europe you would be best advised to look at the EU Regulation starting with Regulation
EU 1178. There are a number of amending regulations, and in addition you should look at the
AMC/GM to the Aircrew Regulation where you will find specific details of the required syllabi.
CAP 804 is a solely UK document and more suited to National requirements. You may complete different parts of the requirements in different States, the one issuing your medical certificate will be the one to whom you apply for the licence/certificate. If you mix and match across the States each module must be completed in that State and you will need a certificate of course completion that you can take to another Sate.