I've been fairly lucky turning up at hotels in the morning. Half the time I have had to wait up to an hour for a room to be made up, but that's better than paying for an extra day or half day. All the other times have just been given a room straight off. Guess it depends on how busy the hotel is and how helpful they want to be. I never expect though, just hope. There have been many times when I have been checking out of hotels in the morning and arriving guests have been told they can't check in until after midday.