It is becoming increasingly common for retired Service personnel (and others) to wear medals at black tie event....and why not! Re the QDJM - there were some 425,000 minted - go figure who might reasonably be wearing them. Miniatures are not official medals so you might see anyone buying a set.
The current First Sea Lord is also encouraging retirees to wear uniform to appropriate events - dinners, Remembrance, weddings etc. For the RN you still hold the Queen's commission, just not on the Active List. Pity about the loss of an ID card though.