The UK ATPL was what the UK CAA issued prior to the UK implementing JAR FCL requirements. They haven't issued UK national licences since 2000 or 2001. Now, the UK CAA is an issuing state for JAR licences. I think my UK (not JAA) ATPL was from near the end of UK licence issuance.
JAA requires a licence to be the responsibility of one of their member states. If your JAA licence was issued by the UK then chances are it has UK blurb on it, even though it's a JAA licence.