My daughter has a feed at 11 in the night and then does not wake up till 5 the next morning. Is it okay? The doctor says it's fine.

Of course it's fine! My daughter also sleeps around 11pm and doesn't wake up until about 6 or 7am when I latch her. She used to wake up around 4am for a feed, but now she just sleeps right through. I wonder what happened, but it's a good problem. If they're hungry, they will definitely let you know.