Article 155 says:
'JAR-FCL 1' means the Joint Aviation Requirement of the JAA bearing that title including Amendment 3 adopted by the JAA on 1st July 2003
Therefore, this has no standing in the UK:
The list of variants which require differences training was actually removed from JAR-FCL 1 earlier this year (to permit it to be updated without having to re-release the entire JAR-FCL 1), and can now be found here on the JAA website.
So the only bit that applies is:
(c) Variants. If the variant has not been flown within a period of 2 years following the differences training, further differences training or a proficiency check in that variant will be required except for types or variants within the SEP class rating.
(1) Differences training requires additional knowledge and training on an appropriate training device or the aeroplane.
The differences training shall be entered in the pilot’s logbook or equivalent document and signed by a CRI/TRI/SFI(A) or FI(A) as appropriate.
(2) Familiarisation training requires the acquisition of additional knowledge
If you have a differences training certificate in your log for one of the stated differences then its valid on a SEP indefinately. For a ME you have to repeat it every two years.
Its there for safety so apply a bit of common sense rather than trying to make things more complicated than they are.