Any member state may choose to ignore the requirements of JAR-FCL and Greece has clearly, and unsurprisingly, elected to do so in accepting the UK CAA exams without a formal agreement with the UK CAA, in accordance with JAR-FCL 1.065(b).
Whlist this is in the financial interests of Greek FTOs, such as Egnatia, it is not in compliance with JAR-FCL and you should be aware that any other member state would be quite within its rights to refuse to recognise a licence issued under these conditions. It is, therefore, in your interest to confirm with your own Authority that it will recognise a licence or rating based on such non-compliant training.