Always wait.
I have however passed a cortege before that the road was 2 lane duel carriageway, slowly I might add, would not class that as overtaking as such. Why would I stay behind a cortege for miles just making all the traffic back up, I see no disrespect in passing a cortege if the road is 2 lane duel carriageway, I would never actually "overtake" on a single lane road however.