One more thing to add about cosmo and hair, they charge more for those early morning sessions. I was married a few years ago so I am not familiar with the current pricing. Back then it was like $100 for the day of the wedding, $150 for the early morning to get to the castle for the pics.
Depending on the timing of your wedding, you may or may not
want to have to get up the next day. If your going to be drinking heavily, some people do, some people don't, that may also reflect when you do the pics. If your having a later in the evening reception verse one that starts in the afternoon, will make a big difference in when your wedding event ends, and possible how much sleep you will get.
About getting the pics done the day of the wedding. Your dress may get a little dirty. Things were still a little damp in the morning as they were spraying down things to get them clean. My dress accumulated a lot more dirt the day of the MK portraits, cound't see it in the pics, but the bottom of the dress was dirty.
Plus, you may want to get your dress steamed again after the early morning pics because you are driven around in a van and will be sitting down, causing wrinkles. You may or may not think that is acceptable to start the wedding portraits the rest of the wedding events.
Connie