Our DS has been in a big boy bed for the last 2 months, in the last week we have noticed that he wakes in the middle of the night.

He turns on his light, leaves his room to get a book and then goes back and closes his door, gets back into bed and reads his book.
We have a day/night clock which solved the problem of him coming to our room too early in the morning, but this is a new issue.
We've noticed his general behavior during the day hasn't been as good as it used to be - not listening, a lot cheekier, spitting etc, and now we know why, he's not getting enough sleep at night.

Every piece of advice I have read is directed at kids who go into parents rooms and says to walk then back to their bed without a fuss. Well he's already in bed!! Haha

Last night my DH heard him at 1am, he confiscated the book and gently told him to go back to sleep, turned off the light and left the room. At 3am we heard him again - my turn! I got up and almost every light was on in the house, he clearly went searching for that book. I went in to his room and took away the toy he had in there, told him to go back to sleep, very sternly. It seems being tougher on him worked, because this time he stayed asleep till 7am.

Any suggestions or experience with this sort of thing? He's never had sleeping issues before, he falls asleep easily and still naps 2 hours in the day. Bed routine had been the same sknce 3 months old.