One thing aircrew should take note of is that if HMRC do a rummage and find contraband on a miitary aircraft, it takes a lot of convincing talk to persude them that as the captain you are not involved. I know this from experience!
After my incident, I found I was the subject of more rummages than could be considered usual. On a return form one detachment, I heard a rumour that one passenger was significantly over his limit. I got everyone on the flight to sign a declaration that they understood the limits and that they were persoanlly responsible for all their excess duty.
One thing I have found is that if you do want to bring in something expensive over the limit, a call to HMRC to discuss it is well worth the time. I have bought in an expensive watch and a set of golf clubs in the past. They seem to appreciate your honesty and are very amenable to come to an arrangement which is usually in your favour.