One of the 'airmen' DFM holders later had some trouble because it was unheard of for groundcrew to have an operational flying medal - but I cannot remember which one !
I'm pretty sure it was the two airmen that flew with Warburton, the book by Tony Spooner (Warburton's War) does mention this.
Both Norman Shirley and Ron Haddon had problems caused by wearing the DFM ribbons as they did not have an aircrew badge and were picked up on this again and again, they both adopted the policy of not wearing the ribbons where they we not known. Norman Shirley believes the reason that they were both offered commissions was to get them out of this predicament.
ISBN0907579434 published by Crecy