DC4 was born at home with a very fast delivery. We had planned a home birth but the midwife arrived too late having got stuck in Friday afternoon traffic. We live abroad, so have no family close to hand and dh's work is an hour's drive. DH arrived home about 15 minutes before the baby was actually born, so I wasn't all alone for the actual birth either.
My three elder children (eldest age 5) were all upstairs napping, though the eldest wasn't asleep. I had gone to get them from school, made them lunch, then decided that the contractions might actually amount to something, put the children to bed and then called midwife and dh.
Everything all went quite quickly from there on. I had enough time to call a friend to ask her to come and pick up my children when they woke, but by the time they woke the baby had already been born.
DH was fantastic and calm, though relatively well prepared having already assisted the births of DC2 and 3 just before the midwife arrived. Just before dh arrived home I had the midwife on the phone who explained that she was completely stuck in traffic, but I strangely didn't feel that worried, and felt fairly sure that if it came down to it I probably could deliver the baby alone, even with all the children upstairs.
But I wouldn't have planned it like that. I was very pleased to see the midwife arrive, who cut the cord, sorted everything out and most importantly was still there when my baby turned momentarily blue an hour after the birth.
My advice to you if the worst comes to the worst: don't panic, be somewhere where the baby won't get hurt if you don't catch it (they are slippery and turn as they come out), and be in touch with someone who can assist you by phone.
Also, when the baby is born, wrap it up warm quickly, and don't worry about cutting the umbilical cord, that can wait until help arrives.