Beth,
Welcome!
Your case sounds similar to mine. The only difference is that it would seem that you have more of a maxillary deficiency than me, and perhaps are not quite as prognathic. My maxillary advancement was 5mm, and my mandibular setback was 7mm. The surgery should be similar. I was in surgery (or in "theatre," as you say across the pond) for 3.5 hours. The surgeon said it should take about two hours per arch, and I guess he didn't have any complications!
I will tell you that the first thing I told them when I woke up was "pain." In the hospital, they gave me morphine through my IV, so I'm sure I was comfortable. By the second day, I was asking the nurse if I could have something not quite as strong as the morphine, so for me, pain wasn't too bad. I've had some ups and downs with it since I came home, but nothing that can't be managed. Your surgeon will probably prescribe something for you before you go to hospital. That way you can have it all ready when you get home. Long story short--the pain is very manageable, just be sure to stay ahead of it with your meds!
Also, you should know that this surgery makes BIG changes to the structure of your face. So, if things are wacky with your bite post-op for a while, it's perfectly normal. The muscles are first of all, recovering from being stretched beyond belief in surgery, and secondly, getting used to the new position of the bite, so it makes perfect sense that they might rebel a bit! I wish I had been alerted about this before surgery, so that my mind would have been more at ease now. I've had problems with my mandible wanting to shift back forward, and rotate back to the right (they also corrected a 3mm assymetry in my chin by rotating my mandible further back to the left). It makes sense, but my surgeon did not really thoroughly explain to me how I might have problems with this. I am so glad I have the opportunity to alert other people of this possibility!
I have to say that the first week was rough, but I would do it all over again, even if I knew what I was about to face. The change in my bite is remarkable! I know that once my treatment is completed, life will be much better for me.
Good luck with everything, and keep us posted.
