Have turned up at LHR T1 for an LHR-HEL flight only to remember, after presenting tickets at check-in. that I am in fact booked SAS LHR-CPH-HEL

Not a biggy, but embarrassing nonetheless.

Also turned up in Shannon and got to hotel - no reservation - got a room OK, but when I called tavel agency "thats because you are booked in a different hotel, as per your request".....our policy hotel was a dive, so chose another nearby....only I forgot, ended up paying for both :-( (well one myself)