Think you are allowed to wear what you like from pilot wings to DSO's . . . . . as long as you are heir to the throne! Impersonating a member of the Armed Forces (i.e. currently serving) IS an offence. As I once gleefully pointed out to a young lad sat opposite me on the train who had spent the previous 3 hours entertaining me with his tales of daring do directed towards the foxy young lady sat next to me. UNfortunately for Pete, "been in and out of the SBS, toughest section of the Army you know" was the final nail in his coffin!
Don't worry, I wasn't ruining a possible trap, the foxy young lady was my then girlfriend, also serving, who was highly entertained by his bu**sh*t