According to the Melon Farmers site, '
Diamonds Are Forever' has been re-classified from a PG to a 12 for the upcoming 50th anniversary Blu-Ray box set
Latest UK Cuts: BBFC cuts and bans
From what I can gather, this new rating is wholly and soully for the film - there are no new extra features which has caused the BBFC to up the limit
Title « British Board of Film Classification