Same here, ours go in late afternoon the day before, and then its an early start the next morning. They sleep, and don't get fed just before slaughter. We also tag just in the trailer, while they are still hunting in the straw for any leftover pig nuts.
Just had a slight problem last time, as we left the trailer electrics connected overnight (there is a short somewhere...), so as not to forget early morning, and the car battery was totally flat. So we had a trailer with two large pigs in that we couldn't even take off the car, and car wouldn't move.... finally managed to get it started (with trailer electrics disconnected!), and OH then drove all the way to the abattoir with no lights on the trailer, just to get there... fortunately no police on the road at this hour of the morning...