Well, I'm someone who would call the ambulance if m/w couldn't get here in time. I would refuse the IV, refuse to be transported (unless in an emergency), but would want to have them here in case the baby needed resuscitating or I hemmorhaged. I might even make them wait in the driveway if I were already pushing. I may very well be able to resuscitate the baby myself, but in the moment, I might panic and would want some back-up, esp back-up with oxygen, if necessary. I know a friend of a friend who was a novice m/w when she homebirthed her second baby and she said that during the pushing stage, she realized that she had no idea what she would do if there was a problem. She was alert enough to know that her mind was blank, but it was indeed blank. Turned out all was fine, but I guess this is one reason why I would not be comfortable with a UC. I'm not trying to convince you either way, Harriet, but wanted to offer the other perspective and support you if you decide that you'd like back-up.
In terms of pre-labor symptoms, I didn't really have the textbook ones either, but I remember clearly that the night before I went into labor, I was desperate to hear some live music. Somewhere in the back of my head was a story of a mom who had gone to a concert to urge her baby out, and I just had this feeling that we needed to be at a concert that night. So we found one, and as we walked from the car to the concert hall, I remember thinking that it was the first time I was truly uncomfortable and ready for my pregnancy to be over. Less than 12 hrs later, my water broke. Hard to say which came first . . . loud music or the beginnings of labor, but I'll be doing that again if we get antsy!