Thanks for the replies everyone.
It's nice to hear what others do. I have a group of friends who all tend to do things the same and they're all pretty strict about a 7 pm bedtime. I have had a few funny looks about Dd not going to bed till 8.30 Nowdays but she sleeps all night and goes to sleep with no probs so it works for us.
My sisters kids have never had set bedtimes due to her DH working late too, and they have always been bad sleepers so I was scared that bedtime might be a factor.
You're right - they so do t read the books. Up again all night from 2 pm last night.