I’ve read a bit about people’s experiences taking film into/out of the UK, though usually most people are going through London. My flight in the beginning of April was Denver to Detroit to Amsterdam to Cardiff (back was the same except switch Salt Lake City for Detroit). I’m not a stranger to taking film on an airplane, but this was my first-ever trip overseas. As an old hand, I’ll echo what others have said before, in that you want to:
-show up early, when there are less people and you’re not in a hurry
-always be polite
-if possible, try to find a line being looked over by someone older, in their 40s or 50s: they’ll actually remember film
-have your film ready to hand over and don’t take up extra time getting it out (I keep mine in a separate ziploc bag in the outside pocket of my carry-on)
Now I’ve heard that the security in the London airports are rude and will never accommodate requests for film to be hand-checked. Thankfully, it was not a problem to or from Cardiff at all…the Delta terminal in Amsterdam, that’s another story, but that was mostly due to my transatlantic flight being delayed and terribly long lines waiting to get to my plane. When flying out of Cardiff, I asked them to be hand-checked and they did seem slightly put out by it, but did acquiesce. There was the standard “the new scanners don’t damage film” spiel, but like I’ve read I just told them politely that I’m still unsure about that and that I preferred them to be hand-checked. They were under the impression that taking the film out of its plastic containers would do more damage than the x-ray scanner, so there is that to deal with, but ultimately it turned out fine.
While not having to go through customs in Amsterdam, I did have to when I reentered the US in Salt Lake City before catching my connecting flight, no problems with hand-checking the film there.