See LASORS A8:
*The UK CAA does not recognise JAR-FCL PPL(A)/ (H)
examinations completed in another JAA Member State
for the purpose of issuance of a UK JAR-FCL PPL(A)/
(H) as these examinations are produced “nationally”
and are not compiled using the JAA Central Question
Bank.
I would expect the same thing to apply for an Hellenic PPL(A).